This Excel spreadsheet presents the simulation of the UR T60/T35 transformer biased differential protection and is built to provide customers, with a tool for excersizing different transformer setups, and test scenarios. The simulation can be used to verify the biased differential settings, the differential and restraint metering on the relay, and the correct operation of the element, under created test conditions.Some rules to follow, when working with the simulation program:1) Please make sure you enter settings or test currents only into the clear boxes on the spreadsheet provided for that!2) Make sure you enter "0" MVA for all windings you don't use in your transformer setup menu.3) Make sure the angle of Winding 1 is "0" and the angles of the other transformer windings are entered With Respect To (WRT) Winding 1 as negative angles.4) Make the settings for the Differential/Restraint characteristic without exceeding their ranges as set on the relay.5) The magnitudes and angles of the injected test currents should be entered as the ones normally received by the relay from the transformer winding CTs.This means for example, that if we have transformer 100MVA, 230kV/69kV Y/D30 degrees, and CT(w1) 500:5, and CT(w2) 1000:5, and we want to simulate balanced conditions(differential current = 0), one can make the transformer setup, and enter the test currents for Winding 1 and Winding 2 as .

shown on the picture bellow:

Note that the angles of the entered test currents for Winding 2, are as they are received and seen by the relay in normal in service conditions, means adding 180 dgreese to the phase shift angle of the power transformer. From the example above, the angles say for phase A of Winding 2 than will be -30 -180 = -210 degrees, phB(W2) = - 150-180 =330, and for ph C(W2) = - 270-180 = -90 degrees

with a tool for excersizing different transformer setups, and test scenarios. The simulation can be used to verify the biased differential settings, the differential

3) Make sure the angle of Winding 1 is "0" and the angles of the other transformer windings are entered With Respect To (WRT) Winding 1 as negative angles.

-30 -180 = -210 degrees, phB(W2) = - 150-180 =330, and for ph C(W2) = - 270-180 = -90 degrees

Nomber of Windings: 2 DIFF / RSTR CHARACTERISTIC W1 W2 W3 W4 W5 W6 DIFFERENTIAL- RESTRAINT GRAPH

Rated(MVA) 100 100 0 0 0 0 Diff. min. PKP 0.20 Slope1 30.0Nom. (kV) 230 69 230 230 230 69 Kneepoint 1 1.50Connection WYE DELTA WYE WYE DELTA WYE Kneepoint 2 6.00 Slope2 95.0Grounding YES NO YES YES NO YESAngle WRT 0 -30 0 0 0 -30CT primary 500 1000 1000 1000 1000 1000 Pre-calculated graph points >>Pre-calculated ratio of the point from the CT sec. tap 5 5 5 5 5 5 Id/Ir, (%) Ph A Ph B Ph C characteristic, corresponding to the same Inom. Prim. 251.0 836.7 0.0 0.0 0.0 0.0 30.0 30.0 30.0 restraint as per the actual Id/Ir ratio. The trip Inom.Sec. 2.510 4.184 0.000 0.000 0.000 0.000 occurs, when the actual Id/Ir ratio,(%) is biggerRotations ABC Magnitude Reference Winding #: 2 than the pre-calculated Id/Ir ratio, (%)

IA IB IC DIFFERENTIAL CURRENTS

W1 Iad Ibd IcdMagnitude 2.51 2.51 2.51 Magnitude 0.000 0.000 0.000Angle 0.0 -120.0 -240.0 Angle -210.0 -330.0 -90.0

W2

Magnitude 4.18 4.18 4.18 RESTRAINT CURRENTSAngle -210.0 -330.0 -90.0 Iar Ibr IcrW3 Magnitude 0.837 0.837 0.837

Magnitude 0.00 0.00 0.00

Angle 0.0 -120.0 -240.0 Actual Differential/Restraint RatioW4 Actual ph A % ph B % ph C %Magnitude 0.00 0.00 0.00 Id/Ir ratio 0.0 0.0 0.0Angle 0.0 -120.0 -240.0

W5 DIFF. OPERATION

Magnitude 0.00 0.00 0.00 NO TRIPAngle 0.0 -120.0 -240.0 Ia Ib IcW6 No trip No trip No tripMagnitude 0.00 0.00 0.00Angle -210.0 -330.0 -90.0

0WYE NO ABC 1DELTA YES ACB 2ZIG-ZAG 3

456

TRANSFORMER SETTINGS AND CTs

TEST CURRENTS ACTUAL VALUES

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

0123456789

1011121314151617181920

Operating Characteristic

Slope characteristics Iad Ibd I restr, pu

I diff, pu