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Example test procedures

1. Export limit test procedure

The export limit test is intended to verify the operation of relays, controllers and inverters designed to limit the export of power and certify the equipment as meeting the requirements of an export-limited DER facility. Tests are provided for digital relay packages and for controllers and inverters that include the intended function.

A. Reverse Power Relay Test

​This version of the export limit test procedure is intended for stand-alone reverse power and underpower relay packages provided to meet the requirements of an export-limited distributed generation facility. It should be understood that in the reverse power application, the relay will provide a trip output with power in the export direction (toward the EDTI distribution system).

Step 1: Power flow test at minimum, midpoint and maximum pickup level settings

Determine the appropriate secondary pickup current for the desired export power flow of 0.5 secondary watts (the agreed-upon minimum pickup setting; assumes 5 amp and 120 V CT/PT secondary). Apply nominal voltage with minimum current setting at zero degrees in the trip direction. Increase the current to pickup level. Observe the relay trip's (LCD or computer display) indication of power values. Note the indicated power level at which the relay trips. The power indication should be within 2% of the expected power. For relays with adjustable settings, repeat this test at the midpoint and maximum settings. Repeat at phase angles of 90, 180 and 270 degrees and verify that the relay does not operate (measured watts will be zero or negative).

Step 2: Leading power factor test

Apply rated voltage to the relay with a minimum pickup current setting (calculated value for system application) and apply a leading power factor load current in the non-trip direction (current lagging voltage by 135 degrees). Increase the current to the relay rated current and verify that the relay does not operate. For relays with adjustable settings, this test should be repeated at the minimum, midpoint and maximum settings.

Step 3: Minimum power factor test

At nominal voltage and with the minimum pickup (or ranges) determined in Step 1, adjust the current phase angle to 84 or 276 degrees. Increase the current level to pickup (about 10 times higher than at 0 degrees) and verify that the relay operates. Repeat for phase angles of 90, 180 and 270 degrees and verify that the relay does not operate.

Step 4: Negative-sequence voltage test

Using the pickup settings determined in Step 1, apply rated relay voltage and current at 180 degrees from tripping direction, to simulate normal load conditions (for three-phase relays, use Ia at 180, Ib at 60 and Ic at 300 degrees). Remove phase-one voltage and observe that the relay does not operate. Repeat for phases two and three.

Step 5: Load current test

Using the pickup settings determined in Step 1, apply rated voltage and current at 180 degrees from the tripping direction, to simulate normal load conditions (use Ia at 180, Ib at 300 and Ic at 60 degrees). Observe that the relay does not operate.

Step 6: Unbalanced fault test 

Using the pickup settings determined in Step 1, apply rated voltage and 2 times rated current, to simulate an unbalanced fault in the non-trip direction (use Va at 0 degrees, Vb and Vc at 180 degrees, Ia at 180 degrees, Ib at 0 degrees and Ic at 180 degrees). Observe that the relay, especially single-phase, does not operate.

Step 7: Time-delay settings test

Apply Step 1 settings and set the time delay to the minimum setting. Adjust the current source to the appropriate level to determine operating time, and compare against calculated values. Verify that the timer stops when the relay trips. Repeat at midpoint and maximum delay settings.

Step 8: Dielectric test

Perform the test described in IEC 414 using 2 kV RMS for 1 minute.

Step 9: Surge withstand

Perform the surge withstand test described in IEEE C37.90.1.

B. Underpower Relay Test

In the underpower application, the relay will provide a trip output when import power (toward the producer's generating facility) drops below the specified power level.

Note: For an underpower relay, pickup is defined as the highest power level at which the relay indicates that the power is less than the approved setting.

Step 1: Power flow test at minimum, midpoint and maximum pickup level settings

Determine the appropriate secondary pickup current for the desired power flow pickup level of 5% of peak load (the agreed-upon minimum pickup setting). Apply rated voltage and current setting at 0 degrees in the direction of normal load current. Decrease the current to pickup level. Observe the relay's (LCD or computer display) indication of power values. Note the indicated power level at which the relay trips. The power indication should be within 2% of the expected power. For relays with adjustable settings, repeat the test at the midpoint and maximum settings. Repeat at phase angles of 90, 180 and 270 degrees and verify that the relay operates properly.

Step 2: Leading power factor test

Using the pickup current setting determined in Step 1, apply rated voltage and rated leading power factor load current in the normal load direction (current leading voltage by 45 degrees). Decrease the current to 145% of the pickup level determined in Step 1 and verify that the relay does not operate. For relays with adjustable settings, repeat the test at the minimum, midpoint and maximum settings.

Step 3: Minimum power factor test

At nominal voltage and with the minimum pickup (or ranges) determined in Step 1, adjust the current phase angle to 84 or 276 degrees. Decrease the current level to pickup (about 10% of the value at 0 degrees) and verify that the relay operates. Repeat for angles 90, 180 and 270 degrees and verify that the relay operates for any current less than rated current.

Step 4: Negative-sequence voltage test

Using the pickup settings determined in Step 1, apply rated relay voltage and 25% of rated current in the normal load direction, to simulate light load conditions. Remove phase-one voltage and observe that the relay does not operate; repeat for phases two and three.

Step 5: Unbalanced fault test

Using the pickup settings determined in Step 1, apply rated voltage and two times rated current, to simulate an unbalanced fault in the normal load direction (use Va at 0 degrees, Vb and Vc at 180 degrees, Ia at 0 degrees, Ib at 180 degrees and Ic at 0 degrees). Observe that the relay, especially single phase, operates properly.

Step 6: Time-delay settings test

Apply Step 1 settings and set the time delay to the minimum setting. Adjust the current source to the appropriate level to determine operating time, and compare against calculated values. Verify that the timer stops when the relay trips. Repeat at midpoint and maximum delay settings.

Step 7: Dielectric test

Perform the test described in IEC 414 using 2 kV RMS for 1 minute.

Step 8: Surge withstand

Perform the surge withstand test described in IEEE C37.90.1.

C. Functional Tests for Inverters and Controllers

Inverters and controllers designed to provide reverse or underpower functions shall be tested to certify the intended operation of this function. Two methods are provided:

Method 1: If the controller uses external current/voltage measurement to determine the reverse or underpower condition, then the controller shall be functionally tested by applying appropriate secondary currents and potentials as described above in 1. A) Reverse Power Relay Test.

Method 2: If external secondary current or potential signals are not used, then unit-specific tests must be conducted to verify that power cannot be exported across the point of common coupling for a period exceeding two seconds. These tests may be factory tests, if the measurement and control points are part of a single unit, or may be provided for in the field.

2. In-rush current test procedure 1

This test will determine the maximum in-rush current drawn by the unit. Two methods are provided:

Locked-rotor method

​Use the test procedure defined in NEMA MG 1 (manufacturer's data is acceptable if available).

Start-up method

Install and set up the generating facility equipment as specified by the manufacturer. Using a calibrated oscilloscope or data-acquisition equipment with appropriate speed and accuracy, measure the current draw at the point of common coupling as the generating facility starts up and comes into parallel with EDTI's distribution system. Start-up shall follow the normal manufacturer-specified procedure. Sufficient time and current resolution and accuracy shall be used to capture the maximum current draw within 5%. In-rush current is defined as the maximum current draw from EDTI during the start-up process, using a 10-cycle moving average. During the test, the utility source, real or simulated, must be capable of maintaining voltage within +/–5% of rated at the connection to the unit under test. Repeat this test five times. Report the highest 10-cycle current as the in-rush current. A graphical representation of the time-current characteristic along with the certified in-rush current must be included in the test report and made available to EDTI.


1 Pacific Gas and Electric Company, Rule 21 – Generating Facility Interconnections, January 5, 2001.

3. Synchronization test procedure

This test verifies that the unit synchronizes within the specified voltage/frequency/phase angle requirements.

The test will start with only one of the three parameters:

  1. voltage difference between the generating facility and EDTI's distribution system,
  2. frequency difference or
  3. phase angle outside of the synchronization specification.

Initiate the synchronization routine and verify that the generating facility is brought within specification prior to synchronization. Repeat the test five times for each of the above three parameters. For manual synchronization with synch-check relay or manual control with auto-synchronization relay, the test must verify that paralleling does not occur until the parameters are brought within specifications.