Reverse-Power Protection Application With Flexible Protection Function; Description - Siemens SIPROTEC 7SJ62 Manual

Functions

2.18 Reverse-Power Protection Application with Flexible Protection Function

2.18 Reverse-Power Protection Application with Flexible Protection
Function
2.18.1

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 by the protection elements can occur on exceeding
or undershooting of the threshold. Possible applications for reverse power protection are set out in Table 2-24.
Table 2-24
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 2-107 gives an example of an industrial control system with internal supply by the illustrated generator.
All illustrated lines and the busbar are indicated in three-phase (excluding the ground connections and the con-
nection to the voltage measurement at the generator). Both feeders 1 and 2 supply the consumers of the cus-
tomer. Usually the industrial customer receives his current from the energy supplier. The generator runs in syn-
chronism, without feeding power. If the power supply company can no longer guarantee the required supply,
the control system is separated from the system of the power supply company and the generator is taking over
the internal supply. In this example the control system is disconnected from the system of the power supply
company as soon as the frequency leaves the nominal range (e.g. 1 - 2% deviation from the nominal frequen-
cy), the voltage exceeds or undershoots a set value, or the generator's active power is fed to the system of the
power supply company. 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 2.9 and 2.6.
296
Overview of reverse power protection applications
Monitoring of the forward power limits of operational equipment
(transformers, lines)
Protection of a local industrial network against reversed feeding into
the energy supply network
Detection of reversed feeding by 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)
Connection of a capacitor bank
Type of Evaluation
Overshooting
C53000-G1140-C207-2, Release date 01.2008
Undershooting
Detection of idling
motors
SIPROTEC, 7SJ62/64, Manual