Siemens siprotec SJ62, Руководство пользователя

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2.6 Voltage Protection 27, 59
142
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
Overvoltage Pro-
tection - Negative
Sequence System
V2 The three-phase voltage transformer connection for the overvoltage protection can be
configured by means of parameter
614 OP. QUANTITY 59
. Either the largest of the
phase-to-phase voltages (
Vphph
) or the negative system voltage (
V2
) are evaluated
as measured quantities. The negative system detects negative sequence reactance
and can be used for the stabilization of the time overcurrent protection. With backup
protection of transformers or generators, the fault currents lie, in some cases, only
slightly over the load currents. To obtain a pickup threshold of the definite time over-
current protection which should be as sensitive as possible, it is necessary to stabilize
the definite time overcurrent protection by the voltage protection.
Overvoltage protection includes 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 PICKUP V2
) and a shorter time delay (address
5007
,
59-2 DELAY
) may be assigned to the upper element (address
5016
,
59-2
PICKUP V2
). There are no clear cut procedures on how to set the pickup values
59-
1 PICKUP V2
or
59-2 PICKUP V2
, as they depend on the respective station con-
figuration. Since the negative sequence voltage V2 corresponds to a phase-ground
voltage, their threshold value must be set as such.
The parameter
5002 59-1 PICKUP
and
5005 59-2 PICKUP
or
5003 59-1 PICKUP
and
5006 59-2 PICKUP
are deleted during configuration of the negative sequence
voltage and the setting values are activated under the addresses
5015 59-1 PICKUP
V2
or
5016 59-2 PICKUP V2
. Be aware that the parameter device
614 OP.
QUANTITY 59
is ignored with single-pole voltage transformer connection and the ac-
tivation of the threshold value for the phase-to-phase voltages takes place. The time
delays of the overvoltage elements are entered at addresses
5004 59-1 DELAY
and
5007 59-2 DELAY
and should be selected to allow the brief voltage spikes that are
generated during switching operations and to enable clearance of stationary overvolt-
ages in time.
Dropout Threshold
of the Overvoltage
Protection The dropout thresholds of the
59-1
element and the
59-2
element can be set via the
dropout ratio r = V
dropout
/V
pickup
(
5117 59–1 DOUT RATIO
or
5118 59–2 DOUT
RATIO
). In this, the following marginal condition always holds for r:
r · (configured pickup threshold )
≤
150 V with connection of phase-to-phase voltages
or
r · (configured pickup threshold )
≤
260 V with connection of phase-to-ground voltages.
The minimum hysteresis is 0.6 V.
Undervoltage Pro-
tection - Positive
Sequence System
V1 The positive sequence component (
V1
) is evaluated for the undervoltage protection.
Especially in case of stability problems, their acquisition is advantageous because the
positive sequence system is relevant for the limit of the stable energy transmission.
Concerning the pickup values, there are not clear cut procedures on how to set them.
However, because the undervoltage protection function is primarily intended to protect
induction machines from voltage dips and to prevent stability problems, the pickup
values will usually be between 60% and 85% of the nominal voltage. Please note that
with frequency deviations of > 5 Hz of the calculated r. m. s value of the voltage will be
too small and the device will perform unwanted operations.
With a three-phase connection and a single-phase connection of a phase-to-phase
voltage the thresholds are set as phase-phase quantities. Since the positive sequence
component of the voltages corresponds to a phase-ground voltage, their threshold
value has to be multiplied with
√
3. With a single-phase phase-to-ground connection
the threshold is set as phase-ground voltage.