Testing of the Limiters in offline (i.e. When the Machine is at stand still).

1. Field Current Maximum Limiter :

a. Preliminary in order to ensure that the value displayed in the micro-terminal for Ifac is correct, measure the milli-volt drop across the FB Shunt & compute the same for rated value in terms of percentage. This computed value should match the value displayed in micro-terminal for Ifac. In case the values are different then calibration for Ifac has to be done.

b. Please note down the Following parameters c. With Generator Terminal voltage at rated value (Uref= 100 %), Note down all the

parameters of DVR as per table.d. Gradually increase terminal voltage by varying the reference value from local panel to a

higher value i.e. in Micro-terminal Uref= 105%.e. With Generator Terminal voltage at 105% of rated value ( Uref= 105 %) , Note down all

the parameters of DVR as per following table.f. Bring back the terminal voltage to rated value i.e. Uref=100%.g. Note down Field current variation from the above reading at 100 & 105 %. In order to

check the intervention/operation of limiter, field current value shall be adjusted within the above two values recorded.

h. After adjusting limiter value (F400) to new value, give step input to Generator voltage from 100 % to 105 %.

i. Check operation / intervention of Field current maximum limiter.j. With the help of dual channel recorder record the limiter intervention. Also check the

operation of output relay at digital output Module.k. With limiter in operated condition, note down all the parameters as per table.l. Restore the limiter values to original as per factory test report or as per site

requirement.

Parameter Before operationof Limiter

After operation of

Limiter

Remarks

U reference Uref .Generator Voltage Ugen

Field Current Ifac

Generator Current Igac

Power PControl Voltage Uc

Reactive Power QParameters to be recorded from micro terminal.

Ref. Module: 50%

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2. Inductive Stator Current Limiter :

a. Check and ensure that the value in micro-terminal for Igac and the generator current meter reading in the control desk display the same value.

b. With Generator Terminal voltage at rated value ( Uref= 100 %) , Note down all the parameters of DVR as per table.

c. Gradually increase terminal voltage by varying the reference value from Micro-terminal. I.e adjust ref. Value Uref= 105%.

d. With Generator Terminal voltage at 105% of rated value (Uref= 105 %), Note down all the parameters of DVR as per following table.

e. Bring back the terminal voltage to rated value i.e. Uref=100%.

f. Note down Generator stator current variation zone hence obtained from reading at 100 & 105 %. In order to check the intervention/operation of limiter, Inductive stator current value shall be adjusted within the above two values recorded.

g. After adjusting limiter value (F430) to new value, give step input to Generator voltage from 100 % to 105 %.

h. Check operation / intervention of Inductive stator current limiter.

i. With the help of dual channel recorder record the intervention. Also check the operation of output relay at digital output Module.

j. With limiter in operated condition, note down all the parameters as per table.

m. Restore the limiter values to original as per factory test report or as per site requirement.

Parameter Before operationof Limiter

After operation of Limiter

Remarks

U reference Uref .

Generator Voltage Ugen

Field Current Ifac

Generator Current Igac

Control Voltage Uc

Power P

Reactive Power Q

Power Factor Cos

6. Capacitive Stator Current Limiter

a. With Generator Terminal voltage at rated value ( Uref= 100 %) , Note down all the parameters of DVR as per table.

b. Gradually reduce terminal voltage by varying the reference value from Micro-terminal. I.e adjust ref. Value Uref= 90%.( Voltages shall be varied as per system conditions)

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c. With Generator Terminal voltage at 105% of rated value ( Uref= 90 %) , Note down all the parameters of DVR as per following table.

d. Bring back the terminal voltage to rated value i.e. Uref=100%.

e. Note down Generator stator current variation zone hence obtained from reading at 100 & 90 %. Hence to check the intervention/operation of limiter, capacitive stator current value shall be adjusted within this zone.

f. After adjusting limiter value (F460) to new value, give step input to Generator voltage from 100 % to 90 %.

g. Check operation / intervention of Capacitive stator current limiter.

h. With the help of dual channel recorder record the intervention. Also check the operation of output relay at digital output card.

i. At limiter operated condition, note down all the parameters as per table.

j. Restore the limiter values to original as per factory test report.

\

Parameter Before operationof Limiter

After operation of Limiter

Remarks

U Reference Uref

Generator Voltage Ugen

Field Current Ifac

Generator Current Igac

Control Voltage Uc

Power P

Reactive Power Q

Power Factor CosF 460 Ind

7. Load Angle Limiter

a. The value of Xq & Xe has to be entered in DVR.Xq (C4A4) = (164.19%) = PuXe (C4A6) = Pu = pu

Procedure for Calculations of Xe & Xd 

1.  Please refer calculations details for " External Network Reactance Xe P.U." 

Xe= (change in vol. Ug/ Ugn) / (change in MVAR/ S)

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Where,

Ug = Generator terminal VoltageUgn= rated generator terminal voltage.S= Rated MVA capacity of generator.

 For reference, the data of BPCL DVR is enclosed. 

Take machine to inductive zone and note down readings as.( all measurements are taken from microterminal)

Power factor= Lag; Ug= 110.00 V AC ( PT volts)

Reactive power Q = Delta act.( Dact) = deg.

Take machine to capacitive zone and note down readings as.( all measurements are taken from microterminal )

power factor= Lead; Ug= V AC;Reactive power Q = %( MVAR lead )Delta act.( Dact) = deg.

 

Calculations

Change in Ug/ Ugn = (U lag - U lead)/ Ugn

=

Change in MVAR = (MVAR lag - MVAR lead)

=

Xe        = (change in vol. Ug/ Ugn) / (change in MVAR/ S)

            =

           = =

2 Xd and Xe Values.

a. For this, refer to the DVR factory test report document, page titled " synchronous machine data & specification of excitation equipment". This sheet gives details about machine synchronous reactance (direct axis unsaturated / quadrature axis). In case the Quadrature axis reactance is not mentioned then the value as given for direct axis unsaturated in the generator data sheet or DVR test report for e.g. 192.26% (1.92 p.u.) then this value of Xd can be assumed.

b. With Generator Terminal voltage at rated value ( Uref= 100 %) , Note down all the parameters of DVR as per following table.

c. Gradually reduce terminal voltage by varying the reference value from Micro-terminal. I.e adjust ref. Value Uref= 90%.( Voltages shall be varied as per system conditions)

d. With Generator Terminal voltage at 105% of rated value ( Uref= 90 %) , Note down all the parameters of DVR as per table.

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e. Bring back the terminal voltage to rated value i.e. Uref=100%.

f. Note down Generator stator current variation zone hence obtained from reading at 100 & 90 %. Hence to check the intervention/operation of limiter, capacitive stator current value shall be adjusted within this zone.

g. After adjusting limiter value (F4A0) to new value, reduce terminal voltage gradually from 100 % to 90 %.

h. Check operation / intervention of load angle limiter at set value.

i. With the help of dual channel recorder record the intervention. Also check the operation of output relay at digital output card.

j. At limiter operated condition, note down all the parameters as per table.

k. Restore the limiter values to original as per factory test report.

Parameter Before

operationof Limiter

After operation of

Limiter

Remarks

U reference Uref is enclosed

Generator Voltage Ugen

Field Current Ifac

Generator Current Igac

Control Voltage Uc

Power P

Reactive Power Q

Power Factor Cos

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