Siemens SIPROTEC 4, User Manual

Page: 133 / 734

The voltage to be evaluated is selected in Power System Data 1 (see Chapter 2.6 Voltage Protection 27, 59 ,
Table 2-11 ).
Overvoltage protection can be turned
ON
or
OFF
, or set to
Alarm Only
at address 5001
FCT 59
.
Undervoltage protection can be turned
ON
or
OFF
or set to
Alarm Only
at address 5101
FCT 27
.
With the protection function
ON
, tripping, the clearing of a fault and fault recording are initiated when the
thresholds are exceeded and the set time delays have expired.
With setting
Alarm Only
no trip command is given, no fault is recorded and no immediate fault annuncia-
tion is shown on the display
Overvoltage Protection with Phase-to-phase or Phase-to-ground Voltages
The largest of the applied voltages is evaluated for the phase-to-phase or phase-to-ground overvoltage protec-
tion.
The threshold values are set in the value to be evaluated (see Chapter
2.6 Voltage Protection 27, 59 ,
Table 2-11 ).
The overvoltage protection has two elements. The pickup value of the lower threshold (address 5002 or 5003,
59-1 PICKUP
, depending on the phase-to-ground or the phase-to-phase voltages, can be assigned a longer
time delay (address 5004,
59-1 DELAY
) and the upper threshold element (address 5005 or 5006,
59-2
PICKUP
) a shorter (address 5007,
59-2 DELAY
) time delay. There are no specific procedures on how the
pickup values are set. However, as the function is mainly used to prevent high insulation damage to system
components and users, the threshold value 5002 , 5003
59-1 PICKUP
lies generally between 110 % and 115
% of the nominal voltage and setting value 5005 , 5006
59-2 PICKUP
at approximately 130 %.
The time delays of the overvoltage elements are entered at addresses 5004
59-1 DELAY
and 5007
59-2
DELAY
, and should be selected in such manner that they make allowance for brief voltage peaks that are
generated during switching operations and also enable clearance of stationary overvoltages in due time.
The choice between phase-to-ground and phase-to-phase voltage allows voltage asymmetries (e.g. caused by
a ground fault) to be taken into account (phase-to-ground) or to remain unconsidered (phase-to-phase)
during evaluation.
i
i
NOTE
During configuration of a single-phase voltage transformer connection (parameter 240
VT Connect.
1ph
not equal to
NO
), parameters 213
VT Connect. 3ph
and 614
OP. QUANTITY 59
are not evalu-
ated. In this case, exclusively parameters 5003
59-1 PICKUP
or 5006
59-2 PICKUP
are relevant for the
threshold values of the overvoltage protection.
Overvoltage Protection - Positive Sequence System V1
In a three-phase voltage transformer connection the positive sequence system can be evaluated for the over-
voltage protection by means of configuring parameter 614
OP. QUANTITY 59
to
V1
. In this case, the
threshold values of the overvoltage protection must be set in parameters 5019
59-1 PICKUP V1
or 5020
59-2 PICKUP V1
.
Overvoltage Protection - Negative Sequence System V2
In a three-phase transformer connection, parameter 614
OP. QUANTITY 59
can determine that the negative
sequence system
V2
can be evaluated as a measured value for the overvoltage protection. The negative
sequence system detects voltage unbalance and can be used for the stabilization of the time overcurrent
protection. In backup protection of transformers or generators, the fault currents lie, in some cases, only
slightly above the load currents. In order to obtain a pickup threshold of the time overcurrent protection that
is as sensitive as possible, its stabilization via the voltage protection is necessary to avoid false tripping.
Overvoltage protection comprises two elements. Thus, with configuration of the negative system, a longer
time delay (address 5004,
59-1 DELAY
) may be assigned to the lower element (address 5015,
59-1-V2
PICKUP
and a shorter time delay (address 5007,
59-2 DELAY
) may be assigned to the upper element
(address 5016,
59-2-V2 PICKUP
). There are not clear cut procedures on how to set the pickup values
59-1-V2 PICKUP
or
59-2-V2 PICKUP
as they depend on the respective station configuration.
Functions
2.6 Voltage Protection 27, 59
SIPROTEC 4, 7SJ62/64, Manual 133
C53000-G1140-C207-8, Edition 08.2016