IMM 8001/8002 – Digital Motor Protection Relay
ICE / CEE
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IMU307-1 GB Ind. B
16
When earth fault detection is done with this type of ring CT, the rated value INo is the nominal value
of the ring CT, i.e. 100 A, and the maximum sensitivity of the earth fault protection is 1 A.
The relay can operate with a 50-turn ring CT (not provided by CEE).
When earth fault detection is done with this type of ring CT, the rated value INo is the nominal value
of the ring CT, i.e. 50 A, and the maximum sensitivity of the earth fault protection is 0.5 A.
Parameters for the ring CT nominal value (100 turns or 50 turns) are assigned in the item "Rated
Values".
Caution :
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as is shown on the connection diagram, it is imperative to run the ground screening through
the ring CT again to avoid measurement of any spurious current flowing in the screen.
Important note :
The equipment is differently configured depending on the type of earth fault current
detection with residual connection (3CTs) or ring CT (ZCT). The label with the
characteristics on the front panel defines the option.
To change configurations, carry out the following operations :
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Extract the electronic module.
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On the left side of the basic case, a 2-position switch can be seen through a square hole.
To configure the device in the residual connection mode :
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set the 3CT/ZCT switch to the 3CT position (= high position).
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configure the device in the 3 CT connection mode in the item "Rated Values".
To configure the device in the ring CT connection mode :
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set the 3CT/ZCT switch to the ZCT position (= low position).
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configure the device in the ZCT connection mode in the item "Rated Values".
3 CT
Z CT
