Chp133 Bbp Ms
Short Description
reb500...
Description
Topic:
Technology and Solutions Protection and Substation Automation
Busbar Protection
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 1
Measurement System
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Busbar Protection – Measurement System Objectives / Overview r r r r r r r
Introduction BBP Requirement BBP Basics Special Condition for the BBP (≠ LP, TP, GP ….) The “problem” on CT Saturation High Impedance Measurement Principle Low Impedance Measurement Principle
CHP133_BBP_MS / 200709 / RW
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q
Example and Features of different Methods / Algorithms q q q q
INX-2 INX-5 REB500 REB670
r Calculation examples: Differential & Restraining Current / Differential Voltage r Open CT / Differential current Supervision r Additional Release / Tripping Criterias r Intertripping
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Introduction q It is extremely important for Busbar Protection applications to have good security since an unwanted operation might have severe consequences
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q The unwanted operation of the Busbar Protection will have the similar effect as simultaneous faults on all power system elements connected to the bus q On the other hand, the BBP has to be dependable as well. Failure to operate or even slow operation in case of a busbar fault can have fatal consequences. Human injuries, power system blackout, transient instability or considerable damage to the surrounding substation equipment and the close- by generators are some of the possible outcomes
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Introduction q A fault on a busbar in the network is relatively seldom: Statistically once in every 20 – 30 years per switchgear q A fault on an overhead line in the network is statistically more than factor 100 higher
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q The life time of busbar protection systems could be more than 30 – 40 years q According to studies all costs to integrate a BBP system will be covered in case of ONE successful trip in it’s life time q Remember: maloperating / unwanted operating as well as non operating BBP system can and have caused blackouts
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BBP Requirements Number the requirements depending on the importance ___ SIMPLE OPERATION (Maintenance & Commissioning) ___ SELEKTIVITY (only the fault affected busbar is allowed to trip)
___ easily EXTENDABLE ___ SENSITIVITY
___ extensive SELFSUPERVISION
___ RELIABILITY (extensive self- supervision)
___ TRIPPING SPEED ___ STABILITY in case of external faults (even with extreme CT saturation)
___ integration of BREAKER FAILURE PROTECTION CHP133_BBP_MS / 200709 / RW
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(additional protection & monitoring functions)
___ MALOPERATION extremely unacceptable ___ matching to all switchgear CONFIGURATIONS ___ low CT REQUIREMENTS
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BBP Basics
Who knows Mr. Kirchhoff ?
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BBP Basics Kirchhoff’s 1st Law: Node Rule
The sum of all
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currents must be zero
I1 + I2 + I3 = Σ I = 0
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BBP Basics Kirchhoff’s 1st Law: Node Rule
If
I1 + I2 + I3 = Σ I
≠ CHP133_BBP_MS / 200709 / RW
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0 ⇒ Fault on the busbar ⇒ Trip circuit breaker
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BBP Basics Differential current measurement
Σ I = I1 + I2 + I3 If
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Σ I > differential current setting ⇒Trip Busbar Protection the measurement (system) has to be phase segregated 3 (4) measurement systems: R; S; T (& special: N)
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BBP Basics External Fault ⇒ No Differential Current
I2
I1
⇒ No Trip
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ΣI
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BBP Basics Internal Fault
⇒ High Differential Current ⇒ Trip
I2
I1
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ΣI
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BBP Basics External Fault – with DC component ⇒ No Differential Current
I2
I1
⇒ No Trip
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ΣI
A DC component will be superimposed if the short circuit does not occur at the voltage peak The DC component will decade with the network time constant τ=L/R
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BBP Basics Internal Fault – with DC component ⇒ High Differential Current ⇒ Trip
I1
I2
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ΣI
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Line
Busbar Transformer
Generator Transformer
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Busbar
Special Condition for the BBP (≠ LP, TP, GP ….)
Protection Zones
G BB
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Special Condition for the BBP (≠ LP, TP, GP ….) All protection system (excl. BBP): The current in the current transformer (CT) due to a fault inside the protection zone is usually higher than the current in the CT due to a fault outside the protection zone. The reason for this is: • In case on a feeder fault (near the busbar) the current in the feeders CT is equal to the sum of all feeder currents connected to the busbar. • In case on a busbar fault the currents in the CTs are limited by the line or transformer reactance.
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I external fault < I internal fault • Stability condition: on relatively low currents - CT saturation unlikely • Tripping condition: on extremely high currents - CT saturation very likely
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Special Condition for the BBP (≠ LP, TP, GP ….) Busbar protection system: The current in the current transformer (CT) due to a fault outside the protection zone is usually higher than the current in the CT due to a fault inside the protection zone. The reason for this is: • In case on a feeder fault (near the busbar) the current in the feeders CT is equal to the sum of all feeder currents connected to the busbar. • In case on a busbar fault the currents in the CTs are limited by the line or transformer reactance.
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I external fault > I internal fault • Stability condition: on extremely high currents - CT saturation very likely • Tripping condition: on relatively low currents - CT saturation unlikely
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CT Saturation ⇒ the CT saturation will produce a differential current which could result in a MALOPERATION
External Fault I2
I1
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ΣI
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CT Saturation External Fault – with DC component ⇒ the CT saturation will produce a differential current which could result in a MALOPERATION
I2
I1
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ΣI
The DC component will increase the saturation
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High Impedance Measurement Principle
q The only BBP system which can handle CT saturation without any other quantity than Idiff (Σ I ) is the High Impedance Protection System.
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q The High Impedance Measurement Principle uses the physical behaviour of the CT saturation to prevent (mal-) operation in case of external fault with (high) CT saturation.
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High Impedance Measurement Principle Principle / Components BB 1
RL1
CT1
Im
U1
I2 I1 Idiff = Σ I
RR
UR
RL2
U2
Im
CT2
UR > 0
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feeder 1 CT secondary reactance
feeder 2 High impedance (input)
Line resistance from CT to relay
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High Impedance Measurement Principle CT refresher course:
U [V]
10’000
1’000
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Magnetizing Curve
100 0.001
0.01
0.1
Excitation or magnetizing current
1
2
Im [A]
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High Impedance Measurement Principle CT refresher course: 10’000
U [V]
Knee point voltage
1’000
(when saturation starts)
Dynamical resistant: du/di = r >
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Magnetizing Curve
100 0.001
0.01
0.1
Excitation or magnetizing current
1
2
Im [A]
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High Impedance Measurement Principle Internal Fault BB 1
RL1
CT1
Im
U1
I2 I1 Idiff = Σ I
RR
UR
RL2
U2
Im
CT2
UR > 0 feeder 2
Principle: CHP133_BBP_MS / 200709 / RW
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feeder 1
An internal fault will immediately result in a differential current and therefore a (high) voltage on the high impedance. The overvoltage relay which is measuring at the high impedance will pick up instantly. The pick up voltage level must be set depending on the lowest possible fault current and the maximum load.
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High Impedance Measurement Principle Internal Fault BB 1
RL1
CT1
Im
U1
I2 I1 Idiff = Σ I
RR
UR
RL2
U2
Im
CT2
UR > 0
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feeder 1
General setting rule: Uset ≤ Uk (since UR max = Uk)
feeder 2 RR = High Impedance (e.g. 2000Ω) UR = Voltage at the high impedance Uk = CT knee point voltage (e.g. 400V) N = CT ratio (e.g. 4000A/1A) Uset = overvoltage pick up setting
• Uset ≤ 400V
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High Impedance Measurement Principle External Fault (without CT saturation) BB 1
RL1
CT1
Im
U1
I2 I1 Idiff = Σ I
RR
UR
RL2 RW U2
Im
CT2
UR > 0 feeder 2
Principle: CHP133_BBP_MS / 200709 / RW
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feeder 1
An external fault (without CT saturation) will practically produce a very low differential current and therefore “no” voltage on the high impedance. The overvoltage relay which is measuring at the high impedance will not pick up.
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High Impedance Measurement Principle External Fault (with CT saturation) BB 1
RL1
CT1
Im
U1
I2 I1 Idiff = Σ I
RR
UR
RL2 RCT U2
Im
CT2
UR > 0
CHP133_BBP_MS / 200709 / RW
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Principle:
feeder 1
feeder 2
In case of CT saturation the secondary reactance of the saturated CT will practically come to zero. Only the secondary resistant RCT (winding resistant) will result (du/di = r I> CHP133_BBP_MS / 200709 / RW
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t
RP
VDR
Trip
Alarm Block
There is also the possibility to insert a current instead of voltage measurement. Advantage: the Ikmin can be set directly in a current value: Ikmin = Iset * N
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High Impedance Measurement Principle Features q simple, sensitive and extremely stable measurement system – CT could theoretically be saturated / pre- magnetised 100% q tripping time around one halfcycle q easily extendable, if the correct CT is available! q CT class TPS (old class X or BS) required – the TPS class defines q the knee point voltage q the magnetising current at half of the knee point voltage q the winding resistance (at 75°C)
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q inexpensive protection system – expensive CTs q all CTs have to be the same type incl. ratio q no other protection devices are allowed in the same CT circuit q therefore no integration of CB Failure Protection etc. is possible
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High Impedance Measurement Principle Features q in case multiple busbar configuration the current switching must be realised mechanically (risk of maloperation during switching; burned / damaged contacts / CTs !). A check zone and therefore a second CT core is strictly required (see following page) q good testing facility of the measurement system but NOT of the current switching logic (which is the sensitive / week part) q the principal is a mix of physical behaviour of the CT and numerical (or mechanical / analogue) current and voltage measurement – it is not possible to realize it 100% numerically (with a low impedance scheme)
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q the possibility to record the CT currents is not given – therefore fault evaluation is not possible
The state of the art: Usually the High Impedance Protection Principle will only be installed in single busbar or 1 ½ CB configuration
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High Impedance Measurement Principle Multiple Busbar with CT Switching and Check Zone I II
X I
II
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X
X
Discriminating Zone
Checkzone
+
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Low Impedance Measurement Principle Additional Quantity (s) to keep the Stability in case of External Fault with CT Saturation q as described in the previous slides the quantity Idiff (Σ I ) is NOT sufficient in a Low Impedance Measurement System to guarantee Stability in case of External Fault with CT Saturation q this additional quantity varies between the products and relay generations
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q some examples of “clever” solutions are shown SIMPLIFIED in the following slides
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Low Impedance Measurement Principle – BBP Type INX-2 – electronic relay generation
Idiff set < | ∑ I | differential current measurement with instantaneous values
Phase Comparison
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phase angle supervision = current direction supervision with instantaneous values
&
t
TRIP CBs
t= integration time
Setting: - Maximum load < Ikmin < minimum short circuit current to prevent false operation in case of shorted CT and to detect lowest possible fault current
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Low Impedance Measurement Principle – BBP Type INX-2
CHP133_BBP_MS / 200709 / RW
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– electronic relay generation Typical INX-2 Feature: q centralised protection system, location in a centralised panel q automatic test cycle which supervises around 50 – 60 % of all HW components in the protection system and will block the system automatically in case of a HW fault q sometimes it is tricky to find faulty components since the fault indication of the automatic test is not very detailed and a lot of modules / electronic cards are available q differential current and phase comparison (phase angle) measurement system which evaluates instantaneous current values. The system includes no special CT saturation detection facility q low CT requirements: 2-3 ms of current signal must be available. This represents 5 times saturation on symmetrical fault currents (see following page) q tripping time around 12ms q integration of CB failure and End fault Protection is possible q installation from around year 1968 – 1985 q at present, the systems are still being extended (relatively seldom) q around 1200 systems are / were installed
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Low Impedance Measurement Principle CT refresher course: Saturation at symmetrical current due to overburdening or to high primary current
A1
3
Ial = 1: current on which the CT starts to saturates
2 1
A2
A3
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0
5 – times saturation means 5 – times Ial
-1 -2 -3
T 0
The areas
5
10ms A1 = A 2 = A 3 = ∫ i(t) • dt
10
15
are equal
t
20 ms
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation
Ikmin < | ∑ I | differential current measurement with instantaneous values
kset < |∑ I | / ∑ | I |
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stabilising / restraining measurement with quantity Ires = ∑ | I | with instantaneous values
CT saturation detection CT saturation detection with instantaneous values
&
t
TRIP CBs
t= integration time
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation
Differential current Idiff= | Σ I |
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Stabilised / Restraint Characteristic
k= 1 k= 0,8
in
r te
n
f al
l u a
no fault
Ikmin 0
t
Setting: - Maximum load < Ikmin < minimum short circuit current to prevent false operation in case of shorted CT and to detect lowest possible fault current - K typically to 0.8
Restraint current IRest = Σ | I |
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation
CHP133_BBP_MS / 200709 / RW
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Internal Fault
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation
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External Fault – without CT saturation
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation
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External Fault – with CT saturation
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation External Fault –
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with CT saturation
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation External Fault –
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with CT saturation
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation
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External Fault – with CT saturation
Depending on the saturation degree; the k – factor is reached for a longer or shorter time. Maloperation is still possible.
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation
CHP133_BBP_MS / 200709 / RW
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External Fault – with CT saturation
Depending on the saturation degree; the k – factor is reached for a longer or shorter time. Maloperation is still possible.
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation
CHP133_BBP_MS / 200709 / RW
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External Fault – with CT saturation
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation
CHP133_BBP_MS / 200709 / RW
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Electronic circuit to generate Blocking Signals”: e.g. Negative Blocking Signal
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation External Fault – with CT saturation
POS BLOCKING SIGNAL (B+)
(B+)
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Neg BLOCKING SIGNAL (B+)
(B-)
The CT saturation detection will send blocking signals: Positive CT saturation blocking signal will block the trip on negative differential current Negative CT saturation blocking signal will block the trip on positive differential current
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation External Fault – with CT saturation
pos (B+)
I diff
neg
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I diff
(B-)
pos (B+)
I diff
neg I diff
(B-)
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation The CT saturation detection will send blocking signals: Positive CT saturation blocking signal will block the trip on negative differential current Negative CT saturation blocking signal will block the trip on positive differential current
Idiff pos B-
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Idiff neg B+
&
t
&
t
≥1 t= integration time
TRIP CBs
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation External Fault – with CT saturation
pos (B+)
I diff
neg
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I diff
(B-)
pos (B+)
I diff
neg I diff
The Stability is maintained
(B-)
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation
CHP133_BBP_MS / 200709 / RW
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External Fault – with CT saturation & full DC offset
(B+)
(B+)
(B+)
(Idiff -)
(Idiff -)
(Idiff -)
(B+)
(Idiff -)
The Stability is maintained BLOCKING METHOD: tripping in case of external fault with CT saturation will be blocked till the next zero crossing is reached
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation Internal Fault – with CT saturation & full DC offset
(Idiff +)
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(B+)
(Idiff +)
(B+)
(Idiff +)
(B+)
TRIP (no blocking) The CT saturation detection will send blocking signals: Positive CT saturation blocking signal will block the trip on negative differential current
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Negative CT saturation blocking signal will block the trip on positive differential current
Low Impedance Measurement Principle – BBP Type INX-5
CHP133_BBP_MS / 200709 / RW
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– static relay generation Typical INX-5 Feature: q centralised protection system, location in a centralised panel q automatic test cycle which supervises around 75 – 85 % of all HW components in the protection system and will block the system automatically in case of a HW fault q easy to find faulty components since the fault indication of the automatic test is very detailed and a small number of modules / electronic cards are available q restrained differential current measurement characteristic which evaluates instantaneous current values. The system includes a CT saturation detection facility: BLOCKING METHOD. A blocking time which is too long delays the tripping command in case of evolving faults (fault evolves from external to internal)
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Low Impedance Measurement Principle – BBP Type INX-5 – static relay generation
CHP133_BBP_MS / 200709 / RW
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Typical INX-5 Feature: q low CT requirements: 2 ms of current signal must be available. This represents 5 times saturation on symmetrical fault currents q tripping time around 12ms q integration of CB failure and End fault Protection is possible q installation from around year 1980 – 2003 q at present, the systems are still being extended frequently q around 800 systems are / were installed
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation
First harmonic (fundamental) filtering by Fourier filter
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Ikmin < | ∑ I | differential current measurement with fundamental current values
kset < |∑ I | / ∑ | I | stabilising / restraining measurement with quantity Ires = ∑ | I | with fundamental current values
&
TRIP CBs
Phase Comparison phase angle supervision = current direction supervision with fundamental current values
The REB500 BBP system will evaluate only the fundamental frequency current signal. This increases accuracy in the case of relatively small, offset differential currents
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation Restrained differential current and phase comparison algorithms which evaluates “only” the fundamental wave of the current signal:
Primary current I1
I1
I2
I1 I1
I2
I2
I2
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I2
0
t
0
t
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation Restrained differential current and phase comparison algorithms which evaluates “only” the fundamental wave of the current signal:
Secondary current
I1
I1
I2
I1 I1
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I2
I2
I2
I1
0
I2
t
0
t
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation Restrained differential current and phase comparison algorithms which evaluates “only” the fundamental wave of the current signal:
Fundamental frequency component
I1
I1
I2
I1 I1
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I2
I2
I2
I1
0
I2
t
0
t
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation Restrained differential current and phase comparison algorithms which evaluates “only” the fundamental wave of the current signal:
I
Fundamental frequency component
Δa
0
t
CHP133_BBP_MS / 200709 / RW
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Δα
The result is a huge amplitude change (Δ a) and a big phase shift (Δ α) between the two current signals which could result in a maloperation in condition of extreme CT saturation
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation Restrained differential current and phase comparison algorithms which evaluates “only” the fundamental wave of the current signal:
Result with extreme CT saturation
CHP133_BBP_MS / 200709 / RW
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I / In
50 IN
t
ms
Ires / In
Restrained differential current algorithm
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation Restrained differential current and phase comparison algorithms which evaluates “only” the fundamental wave of the current signal:
Result with extreme CT saturation
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k
I / In
50 IN
t
ms
t
Restrained differential current algorithm
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation Restrained differential current and phase comparison algorithms which evaluates “only” the fundamental wave of the current signal:
Result with extreme CT saturation
CHP133_BBP_MS / 200709 / RW
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k
I / In
Phase shift Δ α
50 IN
t
ms
t
Phase comparison algorithm
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation
Restrained differential current and phase comparison algorithms which evaluate the fundamental wave of the reconstructed current signal:
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q The REB500 system will evaluate reconstructed fundamental current values (Fourier filtered values). The system will approximate the saturated current values to it’s origin q This is realized with the from ABB patented so called “Maximum Prolongation Algorithm”. With this it can be obtained that the system is never blocked due to CT saturation: UNBLOCKING METHOD
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation
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Maximum Prolongation Algorithm
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation Restrained differential current and phase comparison algorithms which uses the “Maximum Prolongation Algorithm” followed by the fundamental wave filter (Fourier filter) I1
I1
I2
I1 I1
I2
I2
I2
Reconstructed current signal I2
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I1
0
t
0
t
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation Restrained differential current and phase comparison algorithms which uses the “Maximum Prolongation Algorithm” followed by the fundamental wave filter (Fourier filter) I Δa
Fundamental frequency Component of the Maximum Prolongation signal
0
t
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Δα
The result is a relatively small amplitude change (Δ a) and more important a very small phase shift (Δ α) between the two current signals
ABB
Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation
Result using the “Maximum Prolongation Algorithm” with extreme CT saturation
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I / In
50 IN
t
ms
Ires / In
Restrained differential current algorithm
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation
Result using the “Maximum Prolongation Algorithm” with extreme CT saturation
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k
I / In
50 IN
t
ms
t
Restrained differential current algorithm
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation
Result using the “Maximum Prolongation Algorithm” with extreme CT saturation
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k
I / In
Phase shift Δ α
50 IN
t
ms
t
Phase comparison algorithm
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation
Conclusion:
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By prolonging the maximum value, the signal is compensated such that the best possible approximation of the PHASE ANGLE and AMPLITUDE of the origin primary signal is achieved
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Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation
First harmonic (fundamental) filtering by Fourier filter
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maximum prolongation on all CT Current signal
Ikmin < | ∑ I | differential current measurement with reconstructed fundamental current values
kset < |∑ I | / ∑ | I | stabilising / restraining measurement with quantity Ires = ∑ | I | with reconstructed fundamental current values
&
TRIP CBs
Phase Comparison phase angle supervision = current direction supervision with reconstructed fundamental current values
ABB
Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation Measurement Algorithm: Stabilized differential current
k= 1 k= 0,85 Differential current IDiff
r
F
No Fault CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 74
I
e nt
l na
lt u a
Ikmin 0
Restraint Current IRest
ABB
Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation Measurement Algorithm: Phase comparison Case 1: external fault ∆ϕ ≥ 74°
I1
I2
Im
ϕ12 =139°
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 75
Phase difference ∆ϕ
I2 Tripping area
I1
Re
180° No Fault ∆ϕ min = 74°
74° 0° Fall
Im
Internal Fault 1
I1
2
I2
Re ϕ12 =40°
Case 2: internal fault ∆ϕ < 74°
ABB
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 76
Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation Typical REB500 Feature: q decentralised protection system, location might be in a a centralised panel or distributed (e.g. in the feeder protection panels) q continuous self- supervision which supervises around 90 – 95 % of all HW components and SW tasks in the protection system and will block the system automatically in case of a HW / SW fault q very easy to find faulty components since the fault indication of the continuous self- supervision is very detailed and a very small number of modules / electronic cards are available q restrained differential current measurement (INX-5) and phase comparison (phase angle) (INX-2) algorithm which evaluates reconstructed fundamental current values (Fourier filtered values). The system will approximate the saturated current values to it’s origin with a from ABB patented (so called “maximum prolongation”) algorithm: UNBLOCKING METHOD (the system is never blocked due to CT saturation). No problem in case of evolving faults (fault evolves from external to internal)
ABB
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 77
Low Impedance Measurement Principle - BBP Type REB500 – numerical relay generation Typical REB500 Feature: q the restrained differential current measurement; phase comparison (phase angle) measurement and the maximum prolongation algorithm could be activated individually for special application q typical tripping time around 25ms q integration of CB failure and End fault Protection as well as Line & Transformer Protection Functions is possible. Additional measurement functions as event- & disturbance recorder as well as additional release functions like I> or U< are available q low CT requirements: 2 ms of current signal must be available. This represents 5 times saturation on symmetrical fault currents q state of the art: installation from year 1994 – future q over 1500 systems are in service (so far)
ABB
Low Impedance Measurement Principle - BBP Type REB670 – numerical relay generation
• Ikmin < | ∑ I | differential current measurement with RMS current values
‚sset < |∑ I | / ∑ | Iin | stabilising / restraining measurement with quantity Ires = ∑ | Iin | with RMS current values
&
TRIP CBs
ƒ external fault detection CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 78
(decision 1.2 ms after zero crossing) detection internal / external fault with instantaneous / sampled current values
ABB
Low Impedance Measurement Principle - BBP Type REB670
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 79
– numerical relay generation Representation of the protection zone:
ABB
Low Impedance Measurement Principle - BBP Type REB670 – numerical relay generation Calculation of the instantaneous value of the differential current:
Calculation of the instantaneous sum of positive currents:
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 80
Calculation of the instantaneous sum of negative currents:
ABB
Low Impedance Measurement Principle - BBP Type REB670 – numerical relay generation Calculation of the incoming and outgoing currents:
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 81
Calculation of the RMS value of e.g. Iin (same for Iout and Idiff)
ABB
Low Impedance Measurement Principle - BBP Type REB670
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 82
– numerical relay generation Condition at Internal Fault:
ABB
Low Impedance Measurement Principle - BBP Type REB670
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 83
– numerical relay generation Condition at Internal Fault:
sudden split between of RMS Iin and RMS Iout will indicate an internal fault if • & ‚ (Ikmin & s) is fulfilled the protection will trip since ƒ will not see an external fault
ABB
Low Impedance Measurement Principle - BBP Type REB670
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 84
– numerical relay generation Condition at External Fault with CT Saturation:
ABB
Low Impedance Measurement Principle - BBP Type REB670
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 85
– numerical relay generation Condition at External Fault with CT Saturation:
ƒ will detect an external fault within 1.2ms after the Iin zero crossing (before the CT gets into saturation) and will block till the next zero crossing is reached
ABB
Low Impedance Measurement Principle - BBP Type REB670 – numerical relay generation
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 86
Test assembly:
ABB
Low Impedance Measurement Principle - BBP Type REB670 – numerical relay generation
Test values & result: The CT TX war pre- magnetised with a DC current in order to get maximum remanence. Therefore the CT saturates within 1.2 ms!
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 87
The primary test current level was 26kA RMS with the full DC offset
The BBP system REB670 remains fully stable !!!
ABB
Low Impedance Measurement Principle - BBP Type REB670 – numerical relay generation
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 88
Stabilised / Restraint Characteristic
ABB
Low Impedance Measurement Principle - BBP Type REB670 – numerical relay generation Stabilised / Restraint Characteristic Setting: - Maximum load < Ikmin (Diff Oper Level) < minimum short circuit current to prevent false operation in case of shorted CT and to detect lowest possible fault current
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 89
The sensitive (non restraint) operational level is designed to be able to detect internal busbar faults in low impedance earthed power systems: Limited earth fault current to certain level (300 – 2000A)
ABB
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 90
Low Impedance Measurement Principle - BBP Type REB670 – numerical relay generation Typical REB670 Feature: q centralised protection system, location in a centralised panel q continuous self- supervision which supervises the most of the HW components and SW tasks in the protection system and will block the system automatically in case of a HW / SW fault q very easy to find faulty components since a very small number of modules / electronic cards are available q restrained differential current measurement algorithm which evaluates RMS current values. The system can decides within 1.2ms after the zero crossing of the current if the fault is external or internal. In case of external fault the measurement will be blocked till the next zero crossing: BLOCKING METHOD. A blocking time which is too long delays the tripping command in case of evolving faults (fault evolves from external to internal)
ABB
Low Impedance Measurement Principle - BBP Type REB670 – numerical relay generation
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 91
Typical REB670 Feature: q very low (“almost no”) CT requirements: the system was successfully tested with just 1.2 ms of current signal. This represents >> 5 times saturation on symmetrical fault currents q tripping time around one halfcycle q integration of CB Failure, OC protection as well as event- & disturbance recorder, monitoring function is possible q state of the art: installation from year 2005 – future q the system is a consequently further development / improvement of the well proven BBP systems RADSS, REB103, RED521
ABB
Internal fault condition
Calculation examples
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 92
Busbar fault condition single injection
I1 = 1000A
ABB
Internal fault condition
Calculation examples
Low Impedance Low Impedance Measurement System Measurement System REB500
REB670
High Impedance System (with CT ratio: N = 2000A / 1A; Impedance: RR = 2000 Ω; Knee Point V: UK = 400V)
∆ I = + I1
CHP133_BBP_MS / 200709 / RW
∆ Isec = I1/N
= + 1 kA
= + 1 kA
= 1 kA / 2000
= 1 kA
= 1 kA
= 0.5 A
Σ I = + + I1 © ABB Switzerland Ltd. - 93
∆ I = + I1
Σ Iin = + + I1
∆ U = ∆ Isec * RR
= + 1 kA
= + 1 kA
= 0.5A * 2000Ω
= 1 kA
= 1 kA
= 1 kV (spike) à TRIP
ABB
Internal fault condition
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 94
Differential current Idiff= | Σ I |
Calculation examples
k= 1
I
e nt
r
l na
f al n ter In
Ikmin 0
f
R lt u a
lt au
EB
0 50
70 6 B RE
kREB500= 0,85 kREB670= 0,53
no fault Restraint current IRest = Σ | I | Restraint current IRest = Σ | Iin |
►trip measurement system !!! ⇒ ( if I∆ > Ikmin)
ABB
Internal fault condition
Calculation examples
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 95
Busbar fault condition
multiple injection
I1 = 1000A
I2 = 2500A
I3 = 1500A
I4 = 2000A
ABB
Internal fault condition
Calculation examples
Low Impedance Low Impedance Measurement System Measurement System REB500
REB670
High Impedance System (with CT ratio: N = 2000A / 1A; Impedance: RR = 2000 Ω; Knee Point V: UK = 400V)
∆ I = + I1 + I2 + I3 + I4 = + 1 kA + 2.5 kA + 1.5 kA + 2 kA
= + 1 kA + 2.5 kA + 1.5 kA + 2 kA
= 7 kA
= 7 kA
CHP133_BBP_MS / 200709 / RW
Σ I = ++ I1++ I2+ + I3+ + I4 © ABB Switzerland Ltd. - 96
∆ I = + I1 + I2 + I3 + I4
Σ Iin = ++ I1++ I2+ + I3++ I4
= + 1 kA + 2.5 kA + 1.5 kA + 2 kA
= + 1 kA + 2.5 kA + 1.5 kA + 2 kA
= 7 kA
= 7 kA
∆ Isec = I1/N = 7 kA / 2000 = 3.5 A
∆ U = ∆ Isec * RR = 3.5A * 2000Ω = 7 kV (spike) à TRIP
ABB
Internal fault condition
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 97
Differential current Idiff= | Σ I |
Calculation examples
load depending tripping value!!! k= 1
I
e nt
r
l na
f al n ter In
Ikmin 0
f
R lt u a
lt au
EB
0 50
70 6 B RE
kREB500= 0,85 kREB670= 0,53
no fault Restraint current IRest = Σ | I | Restraint current IRest = Σ | Iin |
►trip measurement system !!! ⇒ ( if I∆ > Ikmin)
ABB
External fault condition
Calculation examples e.g. line fault
I1 =
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 98
6000A
I2 =
I3 =
2500A
1500A
I4 = 2000A
ABB
External fault condition
Calculation examples
Low Impedance Low Impedance Measurement System Measurement System REB500
REB670
High Impedance System (with CT ratio: N = 2000A / 1A; Impedance: RR = 2000 Ω; Knee Point V: UK = 400V)
∆ I = + I1 + I2 + I3 + I4
= - 6 kA + 2.5 kA + 1.5 kA + 2 kA
= - 6 kA + 2.5 kA + 1.5 kA + 2 kA
= 0 kA
= 0 kA
Σ I = ++ I1++ I2+ +I3++ I4 CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 99
∆ I = + I1 + I2 + I3 + I4
Σ Iin = + I2+ +I3++ I4
= + 6 kA + 2.5 kA + 1.5 kA + 2 kA
= 2.5 kA + 1.5 kA + 2 kA
= 12 kA
= 6 kA
∆ Isec = I1/N = 0 kA / 2000 =0A
∆ U = ∆ Isec * RR = 0A * 2000Ω = 0 kV à NO TRIP
ABB
External fault condition
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 100
Differential current Idiff= | Σ I |
Calculation examples
k= 1
I
e nt
r
l na
f al n ter In
Ikmin 0
f
R lt u a
lt au
EB
0 50
70 6 B RE
kREB500= 0,85 kREB670= 0,53
no fault Restraint current IRest = Σ | I | Restraint current IRest = Σ | Iin |
►no trip ►stable !!!
ABB
Current transformer failure (Ι)
Calculation examples
during fault condition (Ι)
I1 =
CT shorted !!!
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 101
6000A
I2 =
I3 =
2500A
1500A
I4 = 2000A
ABB
Current transformer failure (Ι)
Calculation examples
Low Impedance Low Impedance Measurement System Measurement System REB500
REB670
High Impedance System (with CT ratio: N = 2000A / 1A; Impedance: RR = 2000 Ω; Knee Point V: UK = 400V)
∆ I = + I1 + I2 + I3 + I4
= - 6 kA + 2.5 kA + 1.5 kA + 0 kA
= - 6 kA + 2.5 kA + 1.5 kA + 0 kA
= 2 kA
= 2 kA
Σ I = + + I1+ + I2 + + I3 + + I4 CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 102
∆ I = + I1 + I2 + I3 + I4
= + 6 kA + 2.5 kA + 1.5 kA + 0 kA = 10 kA
Σ Iin = + + I1
∆ Isec= I1/N = 2 kA / 2000 =1A
∆ U = ∆ Isec * RR
= + 6 kA
= 1A * 2000Ω
= 6 kA
= 2 kV (spike) à TRIP !!!
ABB
Current transformer failure (Ι)
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 103
Differential current Idiff= | Σ I |
Calculation examples
k= 1
I
e nt
r
l na
f al n ter In
Ikmin 0
f
R lt u a
lt au
EB
0 50
70 6 B RE
kREB500= 0,85 kREB670= 0,53
no fault Restraint current IRest = Σ | I | Restraint current IRest = Σ | Iin |
REB500: no trip ►stable REB670: no trip ►stable
ABB
Current transformer failure (ΙΙ)
Calculation examples
during fault condition (ΙΙ)
CT shorted !!! I1 =
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 104
6000A
I2 =
I3 =
2500A
1500A
I4 = 2000A
ABB
Current transformer failure (ΙΙ)
Calculation examples
Low Impedance Low Impedance Measurement System Measurement System REB500
REB670
High Impedance System (with CT ratio: N = 2000A / 1A; Impedance: RR = 2000 Ω; Knee Point V: UK = 400V)
∆ I = + I1 + I2 + I3 + I4
= + 0 kA + 2.5 kA + 1.5 kA + 2 kA
= + 0 kA + 2.5 kA + 1.5 kA + 2 kA
= 6 kA
= 6 kA
Σ I = + + I1+ + I2 + + I3 + + I4 CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 105
∆ I = + I1 + I2 + I3 + I4
Σ Iin = + + I2 + + I3 + + I4
= + 0 kA + 2.5 kA + 1.5 kA + 2 kA
= + 2.5 kA + 1.5 kA + 2 kA
= 6 kA
= 6 kA
∆ Isec= I1/N = 6 kA / 2000 =3A
∆ U = ∆ Isec * RR = 3A * 2000Ω = 6 kV (spike) à TRIP !!!
ABB
Current transformer failure (ΙΙ)
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 106
Differential current Idiff= | Σ I |
Calculation examples
k= 1
I
e nt
r
l na
f al n ter In
Ikmin 0
f
R lt u a
lt au
EB
0 50
70 6 B RE
kREB500= 0,85 kREB670= 0,53
no fault Restraint current IRest = Σ | I | Restraint current IRest = Σ | Iin |
⇒ trip measurement system !!! (worst case condition)
ABB
Current transformer failure (ΙΙΙ)
Calculation examples
during load condition
CT shorted !!! I1 =
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 107
600A
I2 =
I3 =
250A
150A
I4 = 200A
ABB
Current transformer failure (ΙΙΙ)
Calculation examples
Low Impedance Low Impedance Measurement System Measurement System REB500
REB670
High Impedance System (with CT ratio: N = 2000A / 1A; Impedance: RR = 2000 Ω; Knee Point V: UK = 400V)
∆ I = + I1 + I2 + I3 + I4
= + 0 kA + 250 A + 150 A + 200 A
= + 0 kA + 250 A + 150 A + 200 A
= 600 A
= 600 A
Σ l = + + I1+ + I2 + + I3 + + I4 CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 108
∆ I = + I1 + I2 + I3 + I4
Σ Iin = + + I1+ + I2 + + I3 + + I4
= + 0 kA + 250 A + 150 A + 200 A
= + 250 A + 150 A + 200 A
= 600 A
= 600 A
∆ Isec = I1/N = 0.6 kA / 2000 = 1.2 A
∆ U = ∆ Isec * RR = 1.2A * 2000Ω = 2.4kV (spike) à possible TRIP !!!
ABB
Current transformer failure (ΙΙΙ)
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 109
Differential current Idiff= | Σ I |
Calculation examples
k= 1
I
e nt
r
l na
f al n ter In
Ikmin 0
f
R lt u a
lt au
EB
0 50
70 6 B RE
kREB500= 0,85 kREB670= 0,53
no fault Restraint current IRest = Σ | I | Restraint current IRest = Σ | Iin |
⇒ measurement system stable !!! ⇒ differential current alarm !!!
ABB
Open CT / Differential Current Alarm With a Differential Current Supervision it is possible to detect open / missing CTs during load condition The Differential Current Supervision sends a TIME DELAYED ALARM and there is a setting option to BLOCK the Protection system zone selectively (REB670: also Phase selectively)
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 110
The Supervision is able to detect q a missing CT input (e.g. CT circuit not connected to the system) q a wrong CT ratio q a wrong current direction Therefore the PICK UP VALUE of the Differential Current Supervision should be set lower than the lowest possible load current. The time delay 2–5 seconds)
ABB
Open CT / Differential Current Alarm
⇒ the “differential current / Open CT alarm” is able to detect a missing / wrong CT input ⇒ therefore the “differential current alarm” is very important and must not be ignored by the operating personal
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 111
If not, there is a risk of maloperation !!!
ABB
Additional Tripping / Release Criterias
Additional Tripping / Release Criterias are used to get q Additional SECURITY or
The usage is depending on the CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 112
q Additional FAULT LOCATION
CUSTOMERS PHILISOPIE
ABB
Additional Tripping / Release Criterias Measurement System
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 113
Release for SECURITY
& ≥1
TRIP CBs
Tripping for FAULT LOCATION
ABB
Additional Tripping / Release Criterias Measurement System
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 114
Release for SECURITY
& ≥1
TRIP CBs
Neutral Differential Current Measurement
ABB
Additional Tripping / Release Criterias Neutral Differential Current Measurement is designed to be able to detect internal busbar faults in low impedance earthed power systems: Limited earth fault current to certain level (300 – 2000A)
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 115
No Trip for Phase Differential Measurement !!!
ABB
Additional Tripping / Release Criterias Neutral Differential Current Measurement
Δ I = │∑IN │ IRest = ∑│IN │ (IN = Neutral Current)
K = │∑IN │ / ∑│IN │ = IK / IK = 1 CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 116
and therefore:
►TRIP
ABB
Additional Tripping / Release Criterias Measurement System
Check
&
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 117
Zone
≥1
TRIP CBs
Neutral Differential Current Measurement
ABB
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 118
Additional Tripping / Release Criterias Check Zone
ABB
Additional Tripping / Release Criterias
Differential current Idiff= | Σ I |
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 119
Check Zone
k= 1
I
e nt
rn
f al
a
tR l u
EB
50
0
fault
k Ikmin 0
no fault
Restraint current IRest = Σ | I |
ABB
Additional Tripping / Release Criterias Check Zone q The stability factor k must be calculated very carefully !
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 120
q The Phase Comparison Algorithm is not used in the REB500 system
ABB
Additional Tripping / Release Criterias Measurement System
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 121
Over Current
& ≥1
TRIP CBs
Neutral Differential Current Measurement
ABB
Additional Tripping / Release Criterias Over Current Release
Only that feeders on which a settable over current value is reached will be tripped in case of a trip of the busbar protection I>
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 122
I>
I>
I>
I1 =
I2 =
I3 =
I4 =
300A
250A
50A
100A
ABB
Additional Tripping / Release Criterias Over Current Release
Only that feeders on which a settable over current value is reached will be tripped in case of a trip of the busbar protection I>
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 123
I>
I1 = 1000A
I>
I2 = 2500A
I>
I3 = 1500A
I4 = 2000A
ABB
Additional Tripping / Release Criterias Measurement System
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 124
U< Under Voltage
& ≥1
TRIP CBs
Neutral Differential Current Measurement
ABB
Additional Tripping / Release Criterias Under Voltage Release
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 125
The busbar zone which should be tripped must fulfil a settable under voltage value U
U
U
U
ABB
Additional Tripping / Release Criterias Under Voltage Release
CHP133_BBP_MS / 200709 / RW
© ABB Switzerland Ltd. - 126
The busbar zone which should be tripped must fulfil a settable under voltage value U
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