101
Sudden current change function (SCC)
&KDSWHU
&XUUHQW
)LJXUH ([DPSOHRIWKHWULSSLQJORJLFIRUWKHLPSHGDQFHSURWHFWLRQDQGWKHIXQF
WLRQV69&DQG6&&
&DOFXODWLRQV
The parameters for the sudden current change function are set via the local HMI or PST
(Parameter Setting Tool). Refer to the Technical reference manual for setting parame-
ters and path in local HMI.
The setting of the operate value for the sudden change current measuring element di/dt
must be greater than highest expected load current change on the protected line. It is
necessary with an additional margin of at least 10% above the declared inaccuracy of
the current transformer and measuring element.
The setting of the recovery delay t for the sudden change current measuring element
must be greater than the set time delay of the zone which activates the ZnRW-TRIP sig-
nal plus the operate time of the tripping signal.
The current transformer secondary setting current (Is
SEC
) is:
(Equation 47)
where I
SEC
is the secondary rated current of the main CT and I
PRIM
is the primary sec-
ondary rated current of the main CT.
en02000512.vsd
SCC-START
>1
&
START
START
ZnRW-
SVC-
1RWH
7KHWLPHPXVWEHVKRUWHUWKDQWKHGHDGWLPHLQWHUYDOLQFDVHRIDXWRUHFORVLQJ
Is
SEC
I
S EC
I
PRIM
--------------
Is
⋅
=
Summary of Contents for REO 517
Page 10: ... RQWHQWV ...
Page 16: ...6 Introduction to the application manual KDSWHU QWURGXFWLRQ ...
Page 64: ...54 Blocking of signals during test KDSWHU RPPRQ IXQFWLRQV ...
Page 88: ...78 Scheme communication logic ZCOM KDSWHU LQH LPSHGDQFH ...
Page 146: ...136 Unbalance protection for capacitor banks TOCC KDSWHU XUUHQW ...
Page 166: ...156 Dead line detection DLD KDSWHU 3RZHU V VWHP VXSHUYLVLRQ ...
Page 378: ...368 Monitoring of DC analog measurements KDSWHU 0RQLWRULQJ ...
Page 384: ...374 Pulse counter logic PC KDSWHU 0HWHULQJ ...
Page 412: ...402 Serial communication modules SCM KDSWHU DWD FRPPXQLFDWLRQ ...
Page 440: ...430 LED indication module KDSWHU DUGZDUH PRGXOHV ...