Triconex Training
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Triconex Corporation TRICON Hardware
System Grounding
Electrical systems must be connected to ground in order to:
Protect personnel from electric shock. Protect equipment from damage. Protect the site from lightning damage. Ensure the reliability and electrical integrity of the system. To have interference free operation
What is Ground?
It is a connection to the earth, or to something used in place of the earth.
Why do we require a ground?
The ground is required as it is used to establish and maintain the potential of the earth.
TRICON System typically utilizes three (3) separate ground references:
AC safety or chassis ground (protective earth ground) - TRICON Chassis Ground
Signal or Instrument (or Master Reference) ground - TRICON Signal Ground (TSG)
Field loop shield ground
AC Safety ground is applied to each chassis Signal or Instrument (or Master Reference) ground is the field loop power supply return Field loop shield ground is for referencing instrument loop wiring shields typically to instrument or Master Reference ground
TRICON Main Chassis
TRICON Expansion Chassis
AC Safety Ground Bar
TRICON Expansion Chassis
Each chassis MUST BE connected to AC Safety ground to ensure personnel safety!
TRICON Chassis
Each V5 - V8 Digital I/O Term Panel MUST BE connected to AC Safety ground to ensure personnel safety!
Digital Input Term
AC Safety Ground Bar
AC Safety Ground MUST be applied to each chassis (Main, Expansion & RXM) regardless of floating or non-floating systems.
AC Safety Ground MUST be applied to each V5 V8 DI/DO Term Panel. (floating/non-floating) as the V5 - V8 I/O ELCO cables do not have a connecting wire to chassis. Connection to AC Safety Ground for V9 Terms are not required.
AC Safety Ground MUST NOT be applied to AI/AO Term Panels and #3504E.
AC Safety Ground Analog System TRICON Chassis
Isolated +24 Power Supply V+ V-
Once V- is connected to a AI/AO Term Panel, it is connected to the internal TRICON Signal Ground (TSG).
Analog Input Term
AC Safety
If the TRICON RC Clip is installed, TSG is connected to AC Safety Ground via a parallel resistor/capacitor circuit. TSG V- is referenced to AC Safety within millivolts range.
Dedicated Ground Analog System TRICON Chassis
Isolated +24 Power Supply V+ V-
If the TRICON RC Clip is removed, TSG is disconnected from AC Safety Ground. TSG MUST BE connected to a dedicated ground.
Analog Input Terms Dedicated Ground AC Safety
One connection is required and is completed at the Main Chassis location & any remote RXM locations. The dedicated ground is typically considered a quiet earth ground or DCS Master Reference Ground.
Dedicated Ground Analog System TRICON Chassis
Isolated +24 Power Supply V+ V-
Field loop wiring shields are typically connected to TRICON Term Panels. The TRICON Term Panel shield ground screws should be tied to instrument ground or the dedicated ground.
Analog Input Terms Dedicated Ground AC Safety
TRIOCN RC network V5 - V8 System #8300/#8301/#8305/#8306 TRICON Power Modules are equipped with a simple RC network connected between the signal and chassis ground #8300A/#8301A/#8305A/#8306A TRICON Power Modules allows one to disconnect the internal RC network and directly access the TRICON signal ground.
TRIOCN RC network V9 System The RC network is external to the TRICON Power Modules.
TRIOCN RC network Stand-Alone Digital-Only System Connecting the RC jumper will be sufficient
Stand-Alone Analog-Only or Mixed Analog/Digital System Connecting the RC jumper will be sufficient
TRIOCN RC network Integration with DCS If TRICON is a stand-alone digital-only system, connection of the RC jumper (at the power module for V5 to V8) is sufficient If TRICON is a stand-alone analog-only or mixed analog/digital system, a single connection must be made between TRICON signal ground and the common tie point of the DCS signal ground A TriStation Link with model #410x ICM/EICM may cause a problem if the TriStation PC does not share the safety ground connection as the TRICON. Exercise caution especially if the TRICON and the DCS are physically separated or reside in separate buildings. The same problem could also occur with any RS232 connection including any MODBUS connections.
Connecting two pieces of equipment located in different buildings TRICON I/O bus RS-485 connection extended beyond the control room. Current flow via the Shield ground which is not held at a constant, non-varying voltage. Implementing a “floating” ground system.
In most industrial control systems, the return side of the field power supply is directly connected to earth.
Emergency Shutdown (ESD) and Fire & Gas detection applications very often require the I/O system to be "floating". In a floating ground system, the field power supply is not directly connected to earth ground , but is connected to an artificial ground which can be created with a highimpedance resistor voltage divider.
24VDC
+ 24VDC POWER SUPPLY UNIT
TO ETP POWER R1
R2
+ 24VDC POWER SUPPLY UNIT EARTH GROUND
0VDC
The main use of a floating ground system with a suitable Ground Fault Detector allows for the implementation of a "no-fail system". A “no-fail system” is fault-tolerant of any single field-wiring fault to earth ground. These ground faults should be detectable by the GFD, and if repaired in a timely manner, a shutdown or disturbance to the application should be avoided.
The main purpose of a GFD is to detect the presence of an unintentional connection to earth ground, other than that of the fixed high-impedance connection. A GFD should provide some means of alarming upon detecting an ground fault.
The HOLEC GFD has a sensitivity of 20mA minimum (between +ve and -ve), when used with an external 1.2kΩ resistor divider in 24VDC applications. +
+ 24VDC POWER SUPPLY UNIT
R1
R2
+ 24VDC POWER SUPPLY UNIT EARTH GROUND
HOLEC
-
It is common to install multiple GFDs in a system, either one per Marshalling Cabinet or one per termination panel. After a ground fault has been detected, only the field wiring of the points attached to the alarmed GFD needs to be searched for the earth short.
Ground Fault Detection with D.I. Module
DI ETP PS+ + PS-
24VDC
R1
HOLEC
DI MODULE R2
0VDC
EARTH GROUND
Ground Fault Detection with D.I. Module The following limitations apply to the use of GFDs with digital inputs: A GFD always detects ground faults on the positive side of the contact. A GFD always detects ground faults on the negative side of the contact when the contact is closed. When the contact is open, the GFD might not detect the fault.
Ground Fault Detection with D.I. Module
When the contact is open, the impedance of the input circuitry is in series with the fault impedance. If the sum of the impedances exceeds the sensitivity of the GFD, then the GFD might not detect the fault.
Ground Fault Detection with D.O. Module
FROM DO MODULE DO ETP PS+ + PS-
24VDC
R1
R2 0VDC
EARTH GROUND
HOLEC
Ground Fault Detection with D.O. Module The following limitations apply to the use of GFDs with digital outputs: A GFD always detects ground faults on the negative side of the load. A GFD always detects ground faults on the positive side of the load when the load is energized. When de-energized, a GFD might not detect the fault.
Ground Fault Detection with D.O. Module
When de-energized, the impedance of the load is in series with the fault impedance. If the sum of the impedances exceeds the sensitivity of the GFD, then the GFD might not detect the fault.
Ground Fault Detection with A.I. Module
AI ETP 24VDC
PS+ PSR1
R2 0VDC
EARTH GROUND
180
+ Tx
HOLEC 250
Ground Fault Detection with A.I. Module
From test results and the electrical circuit analysis, we confirmed that the accuracy degradation in the presence of a ground fault is inherent in any 4-20mA instumentation loops.
TRICONEX Your supplier for all your Safety and Critical Control Needs
Defects Down Time False Trips
8-POINT ANALOG OUTPUT MODULE
A
S elector Logic
Loop powe r
BACKPLANE
CABLE
TERMINATION PANEL P W RA (22A)
Curre nt loopba ck
P W RB (24A)
DAC RTN (22E)
B
S elector Logic
RTN (24E)
Curre nt loopba ck
DAC OUT1 (2A)
C
S elector Logic
DAC
RTN1 (2E)
Curre nt loopba ck
TERMINATION PANEL
CABLE BACKPLANE
32-POINT ANALOG INPUT MODULES
to s pa re
Mux Is ola tion/filte ring
1
Amp
ADC
Amp
ADC
Amp
ADC
180 ohms 32 Hi-Re f Low-Re f
Note 3
Mux
to othe r points 1
PS1 PS2 32 PS1
Hi-Re f
PS2
Low-Re f
Mux
1
32 Hi-Re f Low-Re f
Types of Power Utility Power Mains Power UPS Clean Floating AC / DC
Types of Earth Connection Clean Earth Dirty Earth Utility Earth Low noise System Computer
Basically on two types of Ground :a) AC - dirty b) DC - clean
System earth Instrument earth
EMC Electromagnetic Compatibility -> Started by the military application 15 yrs ago Use 3 core power cables for optimal line filtering Power source is reference to earth Floating power contains much more noise than earth reference Floating power needs isolation transformer Floating power may drift to any common mode potential Line filtering requires earth connection Impedance if 3 core power is 100 ohms I/A designed by National Electrical Code
Normal and Common mode signals by : potential equalisation Galvanic isolation Shielding Enclosures Signal to noise ratio
GROUNDING the TRICON Expansion Chassis
1/4" Bolt on left side of each chassis Main Chassis
Expansion Chassis
AC Safety Ground
Bus Bar
AC SAFETY GROUND
(Protective Earth)
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