Operating Characteristics - GE GEK-45404F Instructions Manual

Overvoltage relays

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Table Of Contents

Table of Contents

RELAY

VOLTAGE

TYPES

RATINGS

1AV51D

115

IAV51D

199

IAV51D

345

IAV51K

IAV52K

115

IAV52C

199

345

**Minimum pickup volts

The Type IAV51D relay is a low-pickup voltage relay normally used for ground fault protection on

AC rotating machines. It has single-circuit closing contacts that close when the voltage increases to

pickup value, as set on the tap block. The time delay in closing the contacts is determined by the

setting of the time dial at the top of the shaft. The IAV51D has a capacitor and tapped resistor

connected in series with the operating coil. The capacitor is added to tune the circuit, giving a low

pickup voltage at rated frequency. At rated voltage the operating U magnet is highly saturated,

increasing the impedance of the circuit, thus limiting the current to a safe value. The taps on the

resistor are connected to the tap block to provide a four-to-one range of pickup. As shown in the

typical external connection diagram, Fig. 8, this relay is connected to the machine neutral potential

transformer through a closed contact on the auxiliary tripping relay, hence is energized only when a

ground occurs. To obtain still-lower pickup than the normal calibration, it is permissible to insert an

inverted potential transformer between the machine neutral transformer and the relay coil circuit.

The IAV51D has a seal-in element. Time curves are shown in Fig. 11.

The IAV51K relay is similar to the IAV51D except that it has an external capacitor. Time curves are

shown in Fig. 11.

GEK-45404

50 - Cycle Burden at Rated Voltages

TAP**SETTINGS

A(10)

B(15)

C(25)

D(40)

A(16)

B(24)

C(40)

D(64)

A(28)

B(42)

C(70)

D(112)

A(5.4)

B(7.5)

C(12.5)

D(20)

No Taps