NINT-68 ABB wiring module warranty, after-sales, warehouse supply

Description

NINT-68 To measure the basic operating time of the harmonic restrained differential elements,

 Connect an AC current signal to terminals H1 and G1, through a

double-pole single-throw switch.

The second pole of the switch starts a NINT-68 timer circuit which is stopped by

the operation of the relay trip contact. Refer to the figure below for

details.

 Close the switch and set the current level to three (3) times the minimum

pickup value measured earlier.

Slowly increase I2. As I2 is increased, the element will reset when the

differential current drops below the minimum pickup.

As I 2 continues to increase, the element operates again when both the initial slope and the

minimum pickup conditions are satisfied.

 Calculate the initial slope 1 value at this point.

As I 2 increases further, the element may reset again, depending on the setting of the slope

kneepoint. This is caused by the current values moving into the slope 2 region.

 Continue increasing I2 until the element operates again.

 Compute the slope 2 value at this point.

7.5.2.8 Slope Kneepoint

 To measure the approximate kneepoint NINT-68 location, follow the procedure

above, setting I1 equal to the kneepoint.

 Gradually increase I2 until the element resets.

 Calculate the first slope at this point.

This value should be equal to the initial slope setting.

 Increase I2 until the element operates again.

 Calculate the slope at this point.

It should be equal to the final slope.

If the kneepoint is much different than the selected value of I1, the two

values of slope will be the same.

 For an accurate measurement of the kneepoint, select a value of I1 just

above the kneepoint value.

 Increase I2 until the element resets.

 Calculate the slope.

The value should be equal to the initial slope value.

 Increase I1 by a small amount, say 10%, and adjust I2 until a new

operating point is obtained.

 Calculate the slope.

 Repeat until the slope value equals the final slope.

The kneepoint value is the value of the restraint current at which the

slope changed in value.

Note

Keep in mind the effects of auto-configuration on the magnitude of the current signal fed

to the differential elements when conducting the slope kneepoint test.

7.5.2.9 Second Harmonic Restraint

To measure the percentage of second NINT-68 harmonic required to block the operation of the

harmonic-restraint differential elements, use the connection diagram shown below.

Current is supplied as an operating current to the phase A element.

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