Appendix 1: Sepam current input connection diagrams

Phase current input connection schemes

The current input connection of the existing Sepam protection relay could be done according to one of the following diagrams

Variant 1: phase current measurements by 3 x 1 A or 5 A CTs (standard connection)

Description

Connection of 3 x 1 A or 5 A sensors to the CCA630 or CCA634 connector.

The measurement of the 3 phase currents allows the calculation of residual current.

Parameters

Sensor type	5 A CT or 1 A CT
Number of CTs	I1, I2, I3
Rated current (In)	1...6250 A

Variant 2: phase current measurement by 2 x 1 A or 5 A CTs

Description

Connection of 2 x 1 A or 5 A sensors to the CCA630 or CCA634 connector.

The measurement of phase currents 1 and 3 is sufficient to help ensure all the phase current based protection functions.

The phase current I2 is only assessed for metering functions, assuming that I0 = 0.

This arrangement does not allow the calculation of residual current.

Parameters

Sensor type	5 A CT or 1 A CT
Number of CTs	I1, I3
Rated current (In)	1...6250 A

Variant 3: phase current measurement by 3 LPCT type sensors

Description

Connection of 3 Low Power Current Transducer (LPCT) type sensors to the CCA670 connector. The connection of only one or two LPCT sensors is not allowed and causes Sepam to go into fail-safe position.

The measurement of the 3 phase currents allows the calculation of residual current.

Parameters

Sensor type	LPCT
Number of CTs	I1, I2, I3
Rated current (In)	25, 50, 100, 125, 133, 200, 250, 320, 400, 500, 630, 666, 1000, 1600, 2000 or 3150 A

Residual current input connection schemes

The residual current input connection of the existing Sepam protection relay could be done on connector B (CCA 630/CCA634/CCA670) and connector A according to one of the following diagrams:

Variant 1: residual current calculation by sum of 3 phase currents

Description

Residual current is calculated by the vector sum of the 3 phase currents I1, I2 and I3, measured by 3 x 1 A or 5 A CTs or by 3 LPCT type sensors.

See current input connection diagrams.

Parameters

Residual current	Rated residual current	Measuring range
Sum of 3 Is	In0 = In, CT primary current	0.1...40 In0

Variant 2: residual current measurement by CSH120 or CSH200 core balance CT (standard connection)

Description

Arrangement recommended for the protection of isolated or compensated neutral systems, in which very low fault currents need to be detected.

Parameters

Residual current	Rated residual current	Measuring range
2 A rating CSH	In0 = 2 A	0.2...40 A
20 A rating CSH	In0 = 20 A	2...400 A

Variant 3: residual current measurement by 1 A or 5 A CTs and CCA634

Description

Residual current measurement by 1 A or 5 A CTs.

Terminal 7: 1 A CT
Terminal 8: 5 A CT

Parameters

Residual current	Rated residual current	Measuring range
1 A CT	In0 = In, CT primary current	0.1...20 In0
5 A CT	In0 = In, CT primary current	0.1...20 In0

Variant 4: residual current measurement by 1 A or 5 A CTs and CSH30 interposing ring CT

Description

The CSH30 interposing ring CT is used to connect 1 A or 5 A CTs to Sepam to measure residual current:

Connection of CSH30 interposing ring CT to 1 A CT: make 2 turns through CSH primary
Connection of CSH30 interposing ring CT to 5 A CT: make 4 turns through CSH primary.

Parameters

Residual current	Rated residual current	Measuring range
1 A CT	In0 = In, CT primary current	0.1...20 In0
5 A CT	In0 = In, CT primary current	0.1...20 In0

Variant 5: residual current measurement by core balance CT with ratio of 1/n (n between 50 and 1500)

Description

The ACE990 is used as an interface between an MV core balance CT with a ratio of 1/n (50 < n < 1500) and the Sepam residual current input.

This arrangement allows the continued use of existing core balance CTs on the installation.

Parameters

Residual current	Rated residual current	Measuring range
ACE990 - range 1 (0.00578 ≤ k ≤ 0.04)	In0 = Ik.n *	0.1...20 In0
ACE990 - range 2 (0.0578 ≤ k ≤ 0.26316)	In0 = Ik.n *	0.1...20 In0