ABB Relion REC615, Техническое руководство

Страница: 406 / 869

The operation of MFADPSDE is based on multi-frequency neutral admittance
measurement utilizing cumulative phasor summing technique. This concept
provides extremely secure, dependable and selective earth-fault protection also
in cases where the residual quantities are highly distorted and contain non-
fundamental frequency components. MFADPSDE is well-suited for compensated
networks where measurement signals may have such characteristics, for example,
during intermittent earth faults.
MFADPSDE is capable of operating with both low ohmic and higher ohmic earth
faults, where the sensitivity limit is defined with residual overvoltage condition.
This allows earth faults with several kilohms of fault resistance to be detected
in a symmetrical system. The sensitivity that can be achieved is comparable
with traditional fundamental frequency based methods such as the IoCos/IoSin
(DEFxPDEF), Watt/Varmetric (32N) and neutral admittance (21YN).
MFADPSDE is capable of detecting faults with dominantly fundamental frequency
content as well as transient, intermittent or restriking earth faults. MFADPSDE can
be used as an alternative solution to transient or intermittent function INTRPTEF.
MFADPSDE supports Fault direction indication in operate and non-operate direction
which may be utilized during fault location process. The inbuilt transient detector
can be used to identify restriking or intermittent earth faults, and discriminate
them from permanent or continuous earth faults.
The direction of MFADPSDE can be set as forward or reverse. The operation
characteristic is defined by a tilted operation sector, which is universally valid both
in unearthed and compensated networks. The tilt of the operation sector should
be selected based on the measurement errors of the applied residual current and
voltage measurement transformers.
The operating time characteristic is according to the definite time (DT).
The function contains a blocking functionality to block function outputs, timers or
the function itself.
MFADPSDE supports both tripping and alarming mode of operation. For alarming
earth-fault protection application, the function contains a dedicated operation
mode.
MFADPSDE provides reliability and sensitivity of protection with a single function.
This enables simpler implementation of protection schemes as separate fault type
dedicated earth-fault functions and coordination between them are not necessarily
required. Other advantages of MFADPSDE includes versatile applicability, good
selectivity, good sensitivity and easy setting principles.
One instance (stage) of MFADPSDE function is available.
4.2.7.6 Signals
Table 404: MFADPSDE Input signals
Name Type Default Description
Io SIGNAL 0 Residual current
Uo SIGNAL 0 Residual voltage
Table continues on the next page
Protection functions 1MRS758755 C
406 REC615 & RER615
Technical Manual