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1.2
Application Scope
The digital motor protection SIPROTEC 4 7SK80 is suitable as protection and monitoring unit for asynchronous
machines of any size. It can nevertheless also be used in busbar feeders or as line protection in networks with
grounded, low-resistance grounded, isolated or compensated star 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; therefore, the device can be employed universally. The device provides
excellent backup facilities of differential protective schemes of any kind for lines, transformers, generators,
motors, and busbars of all electromotive series.
Protection Functions
The basic function is the motor protection with start-up time monitoring, restart inhibit and load step function.
Additionally, there is a non-directional overcurrent protection with three definite time elements each 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 Curve can be used for the sen-
sitive 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, ov-
ervoltage and undervoltage protection, and ground fault protection for high-resistance ground faults (directional
or non-directional).
External detectors can measure ambient temperatures or coolant temperatures (also possible by means of an
external RTD box).
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 interface.
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 posi-
tion 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 password request).
Processing of interlocking conditions for switching (e.g. switchgear interlocking) can be established with the aid
of integrated, user-configurable logic functions.
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
Introduction
1.2 Application Scope
21
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