239 MOTOR PROTECTION RELAY

7.25”) it is 1601-0060

CONTROL POWER (36/37)

A universal AC/DC power supply is standard. It covers the range 90 to 300 V DC and 70 to

265 V AC at 50/60 Hz. It is not necessary to make any adjustment to the relay as long as

the control voltage falls within this range. A low voltage power supply is available upon a

request of MOD# 501. It covers the range 20 to 60 V DC and 20 to 48 V AC at 50/60 Hz.

Verify from the product identification label on the back of the relay that the control voltage

matches the intended application. Connect the control voltage input to a stable source of

supply for reliable operation. A 2.5 A fuse is accessible from the back of the unit without

opening the relay by sliding back the fuse access door.

PHASE CT INPUTS (1-9)

Current transformer secondaries of 5 or 1 A can be used for current sensing. Each phase

current input has 3 terminals: 5 A input, 1 A input, and common. Select the 1 or 5 A

terminal and common to match the phase CT secondary. Observe the polarity indicated in

the TYPICAL WIRING DIAGRAM, otherwise current measures incorrectly for the 2-phase or

residually connected CT configurations.

CTs should be selected to be capable of supplying the required current to the total

secondary load which includes the 239 relay burden mentioned in Section 1.2:

Specifications at rated secondary current and the connection wiring burden. The CT must

not saturate under maximum current conditions which can be up to 8 times motor full load

during starting or greater than 12 times during a short circuit. Only CTs rated for protective

relaying should be used since metering CTs are usually not rated to provide enough

current during faults.

GROUND CT INPUT (10/11/12)

Ground sensing terminals are labeled 5A, 50:0.025, and COM. Connection depend on the

grounding system and sensitivity required. For high resistance grounded systems that limit

the ground current or in mines where low levels of ground leakage must be detected, use a

separate CT to sense ground current. In this configuration, referred to as zero sequence or

core balance detection, all three phase conductors must pass through the CT window. If

the phase conductors are bundled in a cable with a ground, the ground wire must either

pass outside the ground CT window or be routed back through the window if it passes

through as part of the cable. Shielded and unshielded cable installations are illustrated in

the TYPICAL WIRING DIAGRAM. A ground CT with a ratio of 50:0.025 for sensing primary

ground currents from 0.05 to 15 A is available from GE. Connect this CT to terminals

50:0.025 and COM. If a conventional 5 A secondary CT is used for zero sequence ground

sensing, connect it to the 5A and COM terminals. A 1 A secondary CT can also be used;

however, to prevent readings from being off by a factor of 5, the ground CT primary

setpoint must be adjusted. See Section 4.3.1 CT Inputs on page 4–21 under GROUND CT

PRIMARY for suitable settings in this situation. Due to the low secondary currents, it is

recommended that the ground CT secondary leads be twisted together and routed to the

239 away from high current carrying conductors. NOTE: The 50:0.025 input is only

recommended for resistance grounded systems. Where the system is solidly grounded

or high levels of current are to be detected use the 5A ground input.

For low resistance or solidly grounded systems where higher ground fault currents will

flow, the phase CTs can be residually connected to provide ground sensing levels as low as

20% of the phase CT primary rating. For example, 100:5 CTs connected in the residual

configuration can sense ground currents as low as 20 A (primary) without requiring a

separate ground CT. This saves the expense of an extra CT however 3 phase CTs are

required. If this connection is used on a high resistance grounded system verify that the