Cable Core Balance Current Transformer; General; Requirements; Class Accuracy - Siemens SIPROTEC 7SJ62 Manual

Appendix
A.4 Current Transformer Requirements
A.4.3

Cable core balance current transformer

General

The requirements to the cable core balance current transformer are determined by the function „sensitive
ground fault detection".
The recommendations are given according to the standard IEC 60044-1.

Requirements

Transformation ratio, typical
It may be necessary to select a different transformation ratio to suit the specific
power system and thus the amount of the maximum ground fault current.
Accuracy limiting factor
Minimum power
Maximum connected load
– For secondary current threshold values ≥ 20 mA
– For secondary current threshold values < 20 mA

Class accuracy

Table A-2
Starpoint
Function directional
Function non-directional
For extremely small ground fault currents it may become necessary to correct the angle at the device (see func-
tion description of „sensitive ground fault detection").
614
Minimum required class accuracy depending on neutral grounding and function operating prin-
ciple
isolated
Class 1
Class 3
compensated
Class 1
Class 1
C53000-G1140-C207-2, Release date 01.2008
60 / 1
FS = 10
1.2 VA
≤ 1.2 VA (≤ 1.2 Ω)
≤ 0.4 VA (≤ 0.4 Ω)
high-resistance ground-
ed
Class 1
Class 3
SIPROTEC, 7SJ62/64, Manual