Dir. Intermittent Earth Fault Protection; Functional Description - Siemens SIPROTEC 4 Manual

Functions

2.14 Dir. Intermittent earth fault protection

2.14 Dir. Intermittent earth fault protection
The directional intermittent ground fault protection is designed to selectively detect intermittent ground faults
in compensated or grounded cable systems.
Intermittent ground faults are usually characterized by the following properties:
- Very short high ground current pulses (up to several hundred amperes) with a duration of less than 1 ms;
- They are self-extinguishing and re-ignite within one half period up to several periods, depending on the
power system conditions and the fault characteristic.
- They can persist over longer periods (many seconds to minutes) and develop into static faults.
Such intermittent ground faults are frequently caused by weak insulation, e.g. due to decreased water resis-
tance of old cables.
Ground fault functions based on fundamental component measured values are primarily designed to detect
static ground faults and do not always operate correctly in the event of intermittent ground faults. The func-
tion described here evaluates specifically the ground current pulses and puts them into relation with the
displacement voltage to determine the direction.
Applications
•
Directional protection against intermittent ground faults which occur, e.g. in cables due to poor insula-
tion or water ingress in cable joints.
2.14.1

Functional Description

Activating the Function
The function is only available if the device is equipped with a sensitive ground current input.
For voltage connection 213 VT Connect. 3ph = Vab, Vbc oder Vab, Vbc, Vx or Vab, Vbc, VSyn
oder Vph-g, VSyn and for 250 50/51 2-ph prot = ON, the directional intermittent ground fault protec-
tion is ineffective. V
The function is blocked in case of a measuring voltage failure under the condition that the fuse-failure monitor
is configured for the functioning in a grounded system (see Section
Failure Monitor).
Furthermore, the function can be blocked externally using the binary input signal
204
cannot be formed for these connection types.
0
2.11.1 Measurement Supervision, Fuse-
>dIEF block .
SIPROTEC 4, 7SJ80, Manual
E50417-G1140-C343-A8, Edition 12.2017