ABB RELION Series Technical Manual page 398

Section 4
Protection functions
392
systems. It can be applied for the earth-fault protection of overhead lines and
underground cables.
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.
1MRS758755 A
REC615 and RER615
Technical Manual