Siemens SIPROTEC 4, User Manual

Page: 134 / 734

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.
Dropout Threshold of the Overvoltage Protection
The dropout thresholds of the 59-1 element and the 59-2 element can be configured via the dropout ratio r =
V
Dropout
/V
Pickup
at addresses 5017
59-1 DOUT RATIO
or 5018
59-2 DOUT RATIO
. The following marginal
condition applies to r:
r · (configured pickup threshold) ≤ 150 V with connection of phase-to-phase voltages and phase-to-ground
voltages or
r · (configured pickup threshold) ≤ 260 V with calculation of the measured values from the connected voltages
(e.g. phase-to-phase voltages calculated from the connected phase-to-ground voltages).
The minimum hysteresis is 0.6 V.
Undervoltage Protection - Positive Sequence System V1
The positive sequence component (
V1
) can be 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 no specific notes 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.
The threshold value is multiplied as positive sequence voltage and set to √3, thus realizing the reference to the
nominal voltage.
Undervoltage protection comprises two elements. The pickup value of the lower threshold is set at address
5110 or 5111,
27-2 PICKUP
(depending on the voltage transformer connection, phase-to-ground or phase-
to-phase), while time delay is set at address 5112,
27-2 DELAY
(short time delay). The pickup value of the
upper element is set at address 5102 or 5103,
27-1 PICKUP
, while the time delay is set at address 5106,
27-1 DELAY
(a somewhat longer time delay). Setting these elements in this way allows the undervoltage
protection function to closely follow the stability behavior of the system.
The time settings should be selected such that tripping occurs in response to voltage dips that lead to unstable
operating conditions. On the other hand, the time delay should be long enough to avoid tripping on short-
term voltage dips.
Undervoltage Protection with Phase-to-phase or Phase-to-ground Voltages
In parameter 615
OP. QUANTITY 27
you can determine for undervoltage protection in a three-phase
connection that instead of the positive-sequence system
V1
, the smallest of the phase-to-phase voltages
Vphph
or the smallest phase-to-ground voltage
Vph-n
is configured as a measured quantity. The threshold
values are set in the quantity to be evaluated (see Section 2.6 Voltage Protection 27, 59 , Table 2-11 ).
Undervoltage protection comprises two elements. The pickup value of the lower threshold is set at address
5110 or 5111,
27-2 PICKUP
(depending on the voltage transformer connection, phase-to-ground or
phaseto- phase), while time delay is set at address 5112,
27-2 DELAY
(short time delay). The pickup value of
the upper element is set at address 5102 or 5103,
27-1 PICKUP
, while the time delay is set at address 5106,
27-1 DELAY
(a somewhat longer time delay). Setting these elements in this way allows the undervoltage
protection function to closely follow the stability behavior of the system.
The time settings should be selected such that tripping occurs in response to voltage dips that lead to unstable
operating conditions. On the other hand, the time delay should be long enough to avoid tripping on short-
term voltage dips.
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 615
OP. QUANTITY 27
are not evalu-
ated. In this case, exclusively parameters 5103
27-1 PICKUP
or5111
27-2 PICKUP
are relevant for the
threshold values of the undervoltage protection.
Functions
2.6 Voltage Protection 27, 59
134 SIPROTEC 4, 7SJ62/64, Manual
C53000-G1140-C207-8, Edition 08.2016