Application Scope - Siemens SIPROTEC 4 Manual

Introduction

1.2 Application Scope

1.2 Application Scope
The multi-function numerical overcurrent protection SIPROTEC 4 7SJ80 is used as protection, control and
monitoring unit for busbar feeders. For line protection, the device can be used in networks with grounded,
lowresistance grounded, isolated or a compensated neutral point structure. It is suited for networks that are
radial and supplied from a single source, open or closed looped networks and for lines with sources at both
ends.
The device includes the functions that are usually necessary for protection, monitoring of circuit breaker posi-
tions and control of circuit breakers in single and double busbars; therefore, the device can be employed
universally. The device provides excellent backup protection of differential protective schemes of any kind for
lines, transformers and busbars of all voltage levels.
Protective Functions
Non-directional overcurrent protection (50, 50N, 51, 51N) is the basic function of the device. There are three
definite time elements and one inverse time element for the phase currents and the ground current. For the
inverse time elements, several characteristics of different standards are provided. Alternatively, a user-defined
characteristic can be used for the sensitive ground fault detection.
Further protection functions included are the negative sequence protection, overload protection, circuit
breaker failure protection and ground fault protection.
Depending on the ordered variant, further protection functions are included, such as frequency protection,
overvoltage and undervoltage protection, and ground fault protection for high-resistance ground faults (direc-
tional or non-directional).
Apart from the short circuit protection functions mentioned before, there are further protection functions
possible as order variants. The overcurrent protection can, for example, be supplemented by a directional
overcurrent protection.
The automatic reclosing function enables several different reclosing cycles for overhead lines. An external
automatic reclosing system can also be connected. To ensure quick detection of the fault location after a short
circuit, the device is equipped with a fault locator.
Before reclosing after a three-pole tripping, the device can verify the validity of the reclosure via a voltage
check and/or a synchrocheck. The synchrocheck function can also be controlled externally.
Control Functions
The device provides a control function which can be accomplished for activating and deactivating the switch-
gear via operator buttons, port B, binary inputs and - using a PC and the DIGSI software - via the front inter-
face.
The status of the primary equipment can be transmitted to the device via auxiliary contacts connected to
binary inputs. The present status (or position) of the primary equipment can be displayed on the device, and
used for interlocking or alarm condition monitoring. The number of operating equipments to be switched is
limited by the binary inputs and outputs available in the device or the binary inputs and outputs allocated for
the switch position indications. Depending on the primary equipment being controlled, one binary input
(single point indication) or two binary inputs (double point indication) may be used for this process.
The capability of switching primary equipment can be restricted by a setting associated with switching
authority (Remote or Local), and by the operating mode (interlocked/non-interlocked, with or without pass-
word request).
Processing of interlocking conditions for switching (e.g. switchgear interlocking) can be established with the
aid of integrated, user-configurable logic functions.
Messages and Measured Values; Recording of Event and Fault Data
The operational indications provide information about conditions in the power system and the device. Meas-
urement quantities and values that are calculated can be displayed locally and communicated via the serial
interfaces.
Device messages can be assigned to a number of LEDs on the front cover (allocatable), can be externally
processed via output contacts (allocatable), linked with user-definable logic functions and/or issued via serial
interfaces.
22 SIPROTEC 4, 7SJ80, Manual
E50417-G1140-C343-A8, Edition 12.2017