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MTA Test Procedure

The document outlines the Maximum Torque Angle (MTA) test procedure for verifying the Z1ANG setting in SEL relays, emphasizing the importance of understanding impedance calculations. It details the steps for performing a phase-to-ground MTA test, including monitoring pickup, calculating measured and test impedances, and configuring test methods based on the Z1 Reach setting. The document also provides Excel formulas for impedance calculations to facilitate the testing process.

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satyaveer singh
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31 views3 pages

MTA Test Procedure

The document outlines the Maximum Torque Angle (MTA) test procedure for verifying the Z1ANG setting in SEL relays, emphasizing the importance of understanding impedance calculations. It details the steps for performing a phase-to-ground MTA test, including monitoring pickup, calculating measured and test impedances, and configuring test methods based on the Z1 Reach setting. The document also provides Excel formulas for impedance calculations to facilitate the testing process.

Uploaded by

satyaveer singh
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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C) MTA Test Procedure

The first test you can perform is the Maximum Torque Angle (MTA) test which verifies

the Z1ANG setting. This test is nearly identical to the “MTA Test Procedure” description

in the “3-Phase Line Distance Protection Testing” section earlier in this document which

you can review for more details. We are going to change the phase angle references from

0}180o to 0-360o to make the calculations easier to understand.

You should notice that SEL relays use a common setting (Z1ANG) for all impedance

elements so it could be argued that only one test (3-P, P-P, or P-G) is required to verify the

MTA. Don’t be fooled by the “Z1” in the front of the setting. Z1 stands for positive sequence

impedance and not Zone 1.

Follow the steps below to perform a phase-to-ground MTA test.

1. Determine how you will monitor pickup and set the relay accordingly, if required.

(Pickup indication by LED, output contact, front panel display, etc. See the Relay Test

Procedures section starting on page 109 for details.)

2. Calculate the measured impedance using the calculation described below. This

calculation is the opposite of the calculations described earlier because, in this case,

we are converting the relay-calculated impedance into a measured-impedance. The

previous equations converted a measured-impedance into the relay-calculated

impedance.

()

()

+∠

Ω°=

+°

=Ω°×+°

=Ω°×Ω°







Z2MG ZMeasured
(1 k0M k0A)

1.85 @78.6 ZMeasured

1 0.978@-6.7

ZMeasured 1.85 @78.6 1 0.978@-6.7

ZMeasured 1.85 @78.6 1.975 @-3.31

ZMeasur = ( Ω × Ω) ( ° + °)

=Ω°

ed 1.85 1.975 @ 78.6 -3.31

ZMeasured 3.653 @75.29

The Excel™ formula for this calculation is:

ZAN Compensated Magnitude

=Ohms*SQRT((1+(k0M1*COS(RADIANS(k0A1))))^2+(k0M1*SIN(RADIANS(k

0A1)))^2)

Chapter 15: Line Distance (21) Element Testing

457

ZAN Compensated Angle

=Angle+(DEGREES(TANH((K0M1*SIN(RADIANS(K0A1)))/(1+(K0M1*COS(RADI

ANS(K0A1)))))))

3. Calculate the test impedance using the calculation described below. The test impedance

should not exceed 90% of the measured impedance.

=×

=Ω°×

=Ω°

ZTest ZMeasured 90%

ZTest 3.653 @75.29 90%

ZTest 3.288 @75.29

The Excel™ formula for this calculation is:

ZAN Compensated Magnitude

=0.9*(Ohms*SQRT((1+(k0M1*COS(RADIANS(k0A1))))^2+(k0M1*SIN(RADIANS(

k0A1)))^2))

ZAN Compensated Angle


=Angle+(DEGREES(TANH((K0M1*SIN(RADIANS(K0A1)))/(1+(K0M1*COS(RADI

ANS(K0A1)))))))

4. Calculate the test configuration using one of these test methods:

a. If the Z1 Reach setting is greater than 0.66 Ohms, arbitrarily determine the

maximum amount of current to be applied to the relay. A good rule of thumb for

maximum continuous current for most relays is 10.0A. Calculate the P-N voltage

required to apply the test impedance using the following formula based on Ohm's

Law.

=×

×Ω

VIR

FaultVolts=FaultAmps ZTest

FaultVolts=9.0A 3.288

FaultVolts=29.59V

b. If the Z1 Reach setting is less than 0.66Ω, use the traditional formula described in

this step with a 5.0V voltage setting. If more than 10.0A is required, the test should

be performed as quickly as possible to prevent equipment damage.

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