BECKWITH ELECTRIC M-3425 Instruction Book Download

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6–47

Testing – 6

87 Phase Differential

VOLTAGE INPUTS: Configuration V1

CURRENT INPUTS: Configuration C3

TEST SETTINGS:

Minimum Pickup

Amps

(0.2 to 3.0)

Percent Slope

(1 to 100)

Time Delay

Cycles

(1 to 8160)

Programmed Outputs

OUT

(1 to 8)

Functions 21, 32, 40

Disable

Functions 46, 50, 50/27

Disable

Functions 50DT, 50N

Disable

Functions 51T, 51V, 87GD

Disable

■

NOTE: Although no voltage input is required for the testing of the 87 function, it is suggested that Nominal

Volts be applied to restrain the functions which use both voltage and current inputs for operation.
If other functions operate during these tests, they will need to also be disabled for the test and
enabled after the tests are complete.

Disable functions as shown. See Section 3.2, Initial Setup Procedure/Settings, Configure Relay
Data, for procedure.

Confirm settings to be tested.

Connect inputs in Configuration V1 and C3 as designated above. See Section 6.1, Equipment/Test
Setup for configuration. Set Voltages = Nominal voltage.

Minimum Pickup Test: Set I

= 0 Amps (input 1); press and hold the TARGET RESET button and

slowly increase I

(input 2) until the PHASE DIFF CURRENT 87 LED light goes on (or the pickup

indicator operates on the computer target screen). The current level of operation will be equal to P
amps ±0.1 A or ±5%. Release the TARGET RESET button and decrease the current and the
OUTPUT LEDs will go out. Press TARGET RESET button to remove targets. Each phase may be
tested individually or I

and I

may be exchanged.

Timer Test: With output contacts (Z) connected to stop the timer, apply at least 10% higher I

(input 2) current than the minimum pickup level and start timing. The contacts will close after D
cycles within

1 cycle or 1%. When the Time Delay is set to 1 cycle, the relay operation is less

than 1-1/2 cycles.

Slope Test: Define any number of testing points desirable to verify the trip curve. Choosing any
values for I

(input 1), calculate the expected operating current I

(input 2) according to the

following:

-I

)

Slope/100

÷2

Difference in currents

is greater than sum of the currents times the per unit slope

÷2

or I

= [(1+K) ÷ (1-K)] x I

where K = S/200 and where S is % slope input above.

■

NOTE: For tests above the restraint current {(I

)/2} value of 2X Nominal Current; use a slope % value

equal to 4 times the input slope value (S) for these computations.

With I

(input 1) and I

(Input 2) set at the chosen value, hold the TARGET RESET button in and

slowly increase either current until the PHASE DIFF CURRENT 87 LED light goes on or the
pickup indicator operates on the computer target screen. The current level of operation will equal
to I

within ±0.1 A or ±2% slope calculation. Release the TARGET RESET button and decrease

the larger CURRENT and the OUTPUT LEDs will go out. Press TARGET RESET button to
remove targets. Note that the difference in current must be greater than minimum pickup current
for proper operation.

If testing is complete, enable any functions disabled for this test. If other tests are to be
completed, check the proper functions to disable for the next test and proceed from this
configuration.