Siemens SIPROTEC User Manual

Functions
2.11 Measures for Weak and Zero Infeed
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
275
2.11.2 Classical Tripping
2.11.2.1 Method of Operation
Teleprotection schemes
By coordinating the weak infeed function with the teleprotection in conjunction with distance protection and/or
earth fault protection, fast tripping can also be achieved at both line ends in the above cases.
At the strong infeed line end, the distance protection can always trip instantaneously for faults inside zone Z1.
With permissive teleprotection schemes, fast tripping for faults on 100% of the line length is achieved by acti-
vation of the echo function (see section 2.7).This provides the permissive release of the trip signal at the strong
infeed line end.
The permissive teleprotection scheme in conjunction with the earth fault protection can also achieve release of
the trip signal at the strong infeed line end by means of the echo function (refer to Section 2.9).
In many cases tripping of the circuit breaker at the weak infeeding line end is also desired. For this purpose the
device 7SD5 has a dedicated protection function with dedicated trip command.
Pickup with undervoltage
In Figure 2-141, the logic diagram of the weak-infeed tripping is shown. The function can be activated (ECHO
and TRIP and Echo &Trip(I=0)) or deactivated (OFF) in address 2501 FCT Weak Infeed (W
eak Infeed
FunCTion
). If this „switch“ is set to ECHO only, the tripping is also disabled; however, the echo function to
release the infeeding line end is activated (refer also to Section 2.7 and 2.9). The tripping function can be
blocked at any time via the binary input „>BLOCK Weak Inf“.
The logic for the detection of a weak-infeed condition is built up per phase in conjunction with the distance pro-
tection and additionally once for the earth fault protection. Since the undervoltage check is performed for each
phase, single-pole tripping is also possible, provided the device version has the single-pole tripping option.
In the event of a short-circuit, it may be assumed that only a small voltage appears at the line end with the weak-
infeed condition, as the small fault current only produces a small voltage drop in the short-circuit loop. In the
event of zero-infeed, the loop voltage is approximately zero. The weak-infeed tripping is therefore dependent
on the measured undervoltage UNDERVOLTAGE which is also used for the selection of the faulty phase.
If a signal is received from the opposite line end without fault detection by the local protection, this indicates
that there is a fault on the protected feeder. In the case of three terminal lines when using a comparison
scheme a receive signal from both ends may be present. In the case of underreach schemes one receive signal
from at least one end is sufficient.
After a security margin time of 40°ms following reception of the receive signal, the weak-infeed tripping is re-
leased if the remaining conditions are satisfied: undervoltage, circuit breaker closed and no pickup of the dis-
tance protection or of the earth fault protection.
To avoid a faulty pickup of the weak infeed function following tripping of the line and reset of the fault detection,
the function cannot pick up anymore once a fault detection in the affected phase was present (RS flip-flop in
Figure ).
In the case of the earth fault protection, the release signal is routed via the phase segregated logic modules.
Single-phase tripping is therefore also possible if both distance protection and earth fault protection or exclu-
sively earth fault protection issues a release condition.

Siemens SIPROTEC Specifications

General

Brand	Siemens
Model	SIPROTEC
Category	Protection Device
Language	English

Summary

Introduction

Overall Operation

Describes the basic structure and operation of the line differential protection 7SD5, including analog inputs and microcomputer system.

Application Scope

Details the application scope of the 7SD5 line protection relay, covering differential and distance protection capabilities.

Characteristics

Lists general features of the device, differential protection, distance protection, and power swing supplement.

Functions

General

Provides general information about device settings, interaction with substation, and protection functions.

Protection Data Interfaces and Protection Data Topology

Explains how devices exchange data via protection data interfaces for differential protection.

Differential Protection

Describes the basic principle of differential protection for lines, including multiple ends and transmission of measured values.

Distance Protection (optional)

Details the distance protection function, including general settings, fault detection, and pickup modes.

Power Swing Detection (optional)

Explains the integrated power swing supplement for blocking or tripping during power swings.

Teleprotection for Distance Protection (optional)

Describes teleprotection schemes for achieving instantaneous and selective tripping.

Earth Fault Protection in Earthed Systems (optional)

Covers protection functions for high-resistance earth faults in earthed systems, including overcurrent stages.

Teleprotection for Earth Fault Protection (optional)

Explains how directional earth fault protection can be expanded with directional comparison schemes.

Restricted Earth Fault Protection (optional)

Focuses on detecting earth faults in power transformers with earthed starpoints.

Measures for Weak and Zero Infeed

Addresses protection for line ends with weak or no infeed, including echo and weak infeed tripping.

Direct Local Trip

Explains how external signals can be coupled for local circuit breaker control.

Transmission of Binary Commands and Messages

Describes the transmission of binary information between devices for protection and control.

Instantaneous High-Current Switch-onto-Fault Protection (SOTF)

Details the function for disconnecting feeders switched onto high-current faults immediately.

Sensitive Earth Flt.(comp/ isol. starp.)

Covers earth fault detection in non-earthed or compensated systems, including directional determination.

Backup Time Overcurrent Protection

Describes the integrated time overcurrent protection function for backup or emergency use.

Automatic Reclosure Function (optional)

Explains the integrated automatic reclosure function for overhead lines and its operational modes.

Synchronism and Voltage Check (optional)

Details the function for checking network stability before switching a line onto a busbar.

Undervoltage and Overvoltage Protection (optional)

Covers protection against abnormal voltage conditions like overfrequency and underfrequency.

Frequency Protection (optional)

Explains the function for detecting overfrequencies or underfrequencies in the system.

Fault Locator

Describes the function for measuring the distance to a fault, aiding in fault localization.

Circuit Breaker Failure Protection

Provides rapid back-up fault clearance when the circuit breaker fails to respond to a trip command.

Thermal Overload Protection

Details the function to prevent damage to protected objects caused by thermal overloading.

Monitoring Functions

Covers various monitoring capabilities including hardware, software, and measurement supervision.

Function Control and Circuit Breaker Test

Explains how to control functions and perform circuit breaker tests for optimal device operation.

Mounting and Commissioning

Mounting and Connections

Provides guidelines for the proper mounting and electrical connections of the device.

Checking Connections

Details how to check data connections of serial interfaces, protection data communication, and system connections.

Commissioning

Outlines the procedures for testing the device's functions, including test mode and system interface checks.

Final Preparation of the Device

Covers final steps before device operation, such as checking settings and resetting buffers.

Technical Data

General

Lists general technical data, including analog inputs, current transformer requirements, and voltage inputs.

Protection Data Interfaces and differential protection topology

Details technical data for protection data interfaces and differential protection topology.

Differential Protection

Provides technical data for differential protection, including pickup values and intertripping times.

Restricted Earth Fault Protection (optional)

Lists technical data for restricted earth fault protection, including setting ranges and operating times.

Breaker Intertrip and Remote Tripping- Direct Local Trip

Details technical data for breaker intertrip and remote tripping functions.

Distance Protection (optional)

Provides technical data for distance protection, including earth impedance ratios and pickup modes.

Power Swing Detection (with impedance pickup) (optional)

Lists technical data for power swing detection, including blocking programs and tripping criteria.

Teleprotection for Distance Protection (optional)

Details technical data for teleprotection schemes used with distance protection.

Earth Fault Protection in Earthed Systems (optional)

Covers technical data for earth fault protection, including definite time and inverse time stages.

Teleprotection for Earth Fault Protection (optional)

Lists technical data for teleprotection schemes used with earth fault protection.

Weak Infeed Tripping (classical/optional)

Provides technical data for weak infeed tripping, including undervoltage and time settings.

Weak Infeed Tripping (French Specification/optional)

Details technical data for French specification weak infeed tripping.

Direct Remote Trip and Transmission of Binary Information

Lists technical data for remote trip commands and transmission of binary information.

Instantaneous High-Current Switch-onto-Fault Protection (SOTF)

Provides technical data for the SOTF function, including pickup values and trip times.

Earth fault detection in a non-earthed system

Lists technical data for earth fault detection in non-earthed systems.

Backup Time Overcurrent Protection

Describes technical data for backup time overcurrent protection, including definite and inverse time stages.

Automatic Reclosure Function (optional)

Covers technical data for the automatic reclosure function, including operating modes and times.

Synchronism and Voltage Check (optional)

Provides technical data for synchronism and voltage check functions.

Undervoltage and Overvoltage Protection (optional)

Lists technical data for undervoltage and overvoltage protection stages.

Frequency Protection (optional)

Explains technical data for frequency protection, including pickup values and time delays.

Fault Locator

Describes technical data for the fault locator function, including settings and output.

Circuit Breaker Failure Protection

Lists technical data for circuit breaker failure protection and its initiation conditions.

Thermal Overload Protection

Covers technical data for thermal overload protection, including setting ranges and calculation methods.

Monitoring Functions

Details technical data for various monitoring functions like current symmetry and voltage symmetry.

User-defined Functions (CFC)

Provides technical data for user-defined functions using CFC, including function blocks and limits.

Appendix

Ordering Information and Accessories

Contains information on ordering devices and related accessories, including order codes and interface modules.

Terminal Assignments

Details terminal assignments for panel flush mounting, cubicle mounting, and surface mounting configurations.

Connection Examples

Provides examples for connecting current transformers and voltage transformers for various protection functions.

Default Settings

Lists default settings for LEDs, binary inputs, binary outputs, and function keys.

Protocol-dependent Functions

Explains functions dependent on communication protocols like IEC 60870-5-103, IEC 61850, PROFIBUS, and DNP 3.0.

Functional Scope

Outlines the available functions and their configurations, including distance protection and earth fault protection.

Settings

Provides detailed tables of all parameters and their corresponding settings for various functions.

Information List

Lists all available indications and their associated function numbers and descriptions.

Group Alarms

Lists grouped alarms with their respective functions and descriptions.

Measured Values

Details operational measured values for currents, voltages, power, frequency, and differential protection.