9a9.Gen.capability Curve(Ani.)Mppgcl

GENERATOR OPERATION LIMITS By Pra Pradee deep p Yadav, Dy. Director.

When a manufacturer designs & construct an alternator, It will specify the MCR ( max. continuous rating )of the machine in terms of; 1. Stator current. (9050A) 2. Stator voltage. (15.75KV) 3. Rotor current. (2600A.DC) 4. Rotor voltage. (310V.DC) 5. MW. (210MW) 6. MVA. (247MVA) 7. Power factor. (0.85 lagging) The operation of the generator must be such that none of the design limitations are exceeded as otherwise damage to the generator may result

Principal limitations: 1. Stator current limit. 2. Rotor current limit. 3. MW limit. 4. Stability limit. 5. Stator end heating limit.

Capability curve :

Assumption: Generator terminal voltage is maintained constant Erect a voltage vector “OA”.

Principal limitations: 1. Stator current limit : Heat developed in the winding is limited by the class of Insulation. At higher current, overheating may damage insulation. Class “B” Insulation

- 130 Deg. Cel.

Class “F” or “H”

- 180 Deg. Cel.

.

°

Coolent:

Normal

Limit

Property

Cold Hydrogen gas temp. 44 Deg.cel

55Deg.cel 3.5Kg/cm2. 99% pure

Stator water temp.

48 Deg.cel 27m3 /hr.

45 Deg.cel

Rotor angle ()= 90° - Theoritical stability limit. Practical stability limit () = 75°.

1.Variation of terminal voltage:  Voltage(KV) 14.18 14.96 15.75 16.54 16.7 16.85 17.01 17.17 17.32 ------------------------------------------------------------------------------------------------Stator Current(KA)9.5

9.5

9.05

8.6

8.37 8.14

7.92

7.56

7.24

2.Frquency variation: +5%, -5% 3. Overloading: Stator current(KA) 9.95 10.41 10.86 11.31 11.76 12.22 12.67 13.57 Rotor current(KA) 2.75 --

--

---

3.12 --

3.9

5.2

Time ( Sec. )

360

300

240

120

60

3600 900

180

4.Operation at different Hydrogen pressure: Hydrogen Pr.(Kg./Cm 2)

M.W.

Duration

3.0

200

Continous

2.5

170

Not more than 5 Hrs.

2.0

140

-------do------

6.One gas cooler out of service – 175 MW continously. More than one gas cooler out – operation not permitted. Coolent:

Normal

Limit

Property

Cold Hydrogen gas temp. 44 Deg.cel

55Deg.cel 3.5Kg/cm2. 99% pure

Stator water temp.

48 Deg.cel 27m3 /hr.

45 Deg.cel