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Sepam "I0" (Io) inputs for CSH30 and CSH120 / CSH200 - can I perform secondary injection tests on these inputs for Series 20, 40, and 80 relays?

This FAQ gives additional details regarding the "I0" (Io) inputs on the Sepam 20, 40, and 80 relays that are dedicated to Residual Current measurement.

During commissioning or maintenance periods at certain sites, the user may wish to perform secondary injection tests on the Sepam analog measurement channels in order to verify proper operation of the relay.  For example, an OMICRON relay tester can be used to inject current to the inputs on the Sepam CCA630 or CCA634 current transformer module.

However, it is important to note that this is not permitted for the inputs that are dedicated to Residual Current measurement with a CSH120 / CSH200 core-balance CT or the CSH30 interposing CT.  For example, as shown in the screen capture below taken from the Sepam Series 40 manual, notice that for the terminals 18 and 19 on the "A" connector, the only connections allowed to the Sepam are from the following devices:

1) the secondary output of a CSH120 or CSH200 core-balance CT

2) the output from the Sepam ACE990 core-balance CT adaptor module

3) the secondary output from the CSH30 interposing CT

It is not possible to directly connect the 1A or 5A secondary of a standard CT to the "I0" terminals on a Sepam relay.  This input has been designed specifically to accept the output from either a CSH120 / CSH200 sensor, a CSH30 interposing CT, or the ACE990.  Directly connecting the secondary of a standard 1A or 5A CT to this input will damage the Sepam circuitry and void the product warranty.

Users wishing to perform injection tests on the "I0" input of Sepam 20, 40, and 80 relays should first connect a CSH30, CSH120, CSH200, or ACE990 to the input, then inject at the primary side of these sensors or adaptors.  No other practice is authorized by Schneider Electric.  Additionally, since the I0 input is designed to be used only with the approved accessories described here, Schneider Electric does not publish any detailed electrical characteristics for the I0 input itself.

To summarize, any injection tests of the dedicated "I0" input should be performed by first connecting one of the mandatory sensors or adaptors, then injecting a signal into the primary of the accessory.


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