Switching Device; Contactor Current Supervision - GE 339 Instruction Manual

S2 SYSTEM SETUP

Switching device

Contactor current
supervision
6–28
SWITCHING DEVICE
Range: Breaker, Contactor
Default: Breaker
The 339 relay supports both BREAKER and CONTACTOR: the selection of BREAKER or
CONTACTOR here is automatically applied to:
– S5 \Inputs\Outputs\Output Relays
– S4 \Controls\Breaker Control
– S4 \Controls\Breaker Failure
– Maintenance: M4 BKR MAINTENANCE and M4 BKR MONITOR features are
removed when CONTACTOR is selected as SWITCHING DEVICE.
– Assignable output relays for all protection and control elements.
When the SWITCHING DEVICE is selected as BREAKER, the assignable output relays will
be Output Relay 4 to 6. When the SWITCHING DEVICE is selected as CONTACTOR, the
assignable output relays will be Output Relay 5 to 6.
52a CONTACT
Range: Disabled, Enabled
Default: Disabled
The 52a contact function is permanently assigned to contact input number 1. It in single-
speed applications, when enabled, closure of this contact informs the relay that the
motor is connected to the line (online) and therefore the motor is running. It is
recommended that this contact be connected to a form-a (normally open) auxiliary
contact of the breaker/contactor, to ensure the relay maintains running status when
motor current draw is very low. The 52b contact (see below) has the same function, and
is for use when only a form-b (normally closed) auxiliary contact is available.
In two-speed applications, this contact is intended for monitoring the circuit breaker
where there is a circuit breaker as well as a high speed contactor and a low speed
contactor. When enabled and closed, and when one of the contactors is closed, the relay
maintains running status even when the motor current is very small.
52b CONTACT
Range: Disabled, Enabled
Default: Disabled
The 52b contact function is permanently assigned to contact input 2. It performs the
same function as the 52a contact, but with a form-b (normally closed) rather than a
form-a (normally) auxiliary contact of the breaker/contactor.
If both 52a contact and 52b contact are enabled, the relay assumes the motor online if
the 52a contact is closed and the 52b contact is open.
In some cases, the fault current can exceed the current which the contactor is rated to
interrupt. If such a condition has been detected, the 339 blocks the operation of output
relay 1 "Trip" and operates a selected auxiliary output relay. The same auxiliary output
relay must be wired to the upstream switching device (usually a breaker) that is rated to
interrupt the fault current. Finally, if the current has not decreased below the contactor
rated current for a programmable time, the block to output relay 1 is removed.
The sequence described above is intended to prevent damage to the contactor. In order to
use this sequence, configure the following:
• a Short Circuit element
• a Logic Element
• an auxiliary relay
339 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 6: SETPOINTS