Reverse-Power Protection Application With Flexible Protection Function; Description - Siemens SIPROTEC 7SK80 Manual

Functions

2.14 Reverse-Power Protection Application with Flexible Protection Function

2.14 Reverse-Power Protection Application with Flexible Protection
Function
2.14.1

Description

General
By means of the flexible protection functions, a single-element or multi-element reverse power protection can
be realized. Each reverse power element can be operated in single-phase or three-phase. Depending on the
chosen option, the elements can evaluate active power forward, active power reverse, reactive power forward
or reactive power reverse as measured value. The pickup of the protection elements can occur on exceeding
or falling below a threshold. Possible applications for reverse power protection are set out in Table 2-14.
Table 2-14
Direction
P forward
reverse
Q forward
reverse
The following example depicts a typical application where the flexible function acts as reverse power protection.
Disconnection Facility
Figure 2-78 gives an example of an industrial substation with self-supply via the illustrated generator. All illus-
trated lines and the busbar are three-phase (except for the ground connections and the connection to the
voltage measurement at the generator). Both feeders 1 and 2 supply the consumers of the customer. Usually
the industrial customer receives his current from the power supply company. The generator runs synchronously
without feeding power. If the power supply company can no longer guarantee the required supply, the substa-
tion is to be separated from the power supply company's system and the generator to take over the self-supply.
In this example, the substation is to be disconnected from the power supply company's system as soon as the
frequency leaves the nominal range (e.g. 1 - 2% deviation from the nominal frequency), the voltage exceeds
or falls below a set value, or the generator's active power is fed back into the power supply company's system.
Depending on the user's philosophy, some of these criteria may be combined. This would be realized via the
CFC.
The example illustrates how a reverse power protection is implemented by means of the flexible protection
functions. Frequency protection and voltage protection are described in Sections 2.8 and 2.5.
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Overview of reverse power protection applications
Monitoring of the forward power limits of operational equipment (trans-
formers, lines)
Protection of a local industrial network against feedback into the
power supply network
Detection of feedback from motors
Monitoring of the reactive power limits of operational equipment
(transformers, lines)
Connection of a capacitor bank for reactive power compensation
Monitoring of the reactive power limits of operational equipment
(transformers, lines)
Disconnection of a capacitor bank
Type of evaluation
Exceeding
E50417-G1140-C344-A4, Release date 08.2010
Falling below
Detection of idling
motors
SIPROTEC, 7SK80, Manual