Rơ le bảo vệ chênh lệch dòng Line Current Differential Relay - SEL - SEL-311L

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Rơ le bảo vệ chênh lệch dòng Line Current Differential Relay - SEL - SEL-311L

Các dòng sản phẩm thông dụng:

311L#01
- Line current differential relay
- Electromechanical relay retrofit
- Horizontal rack mount

311L#02
- Line current differential relay
- Electromechanical relay retrofit
- Horizontal panel mount

311L#03
- Line current differential relay
- Single-pole differential and single-pole Zone 1 distance protection Additional inputs/outputs and IEC 61850 for easy integration
- Horizontal rack mount

311L#04
- Line current differential relay
- Single-pole differential and single-pole Zone 1 distance protection
- Additional inputs/outputs and IEC 61850 for easy integration
- Horizontal panel mount


 

Line Current Differential Protection and Automation System

Use the SEL-311L Line Current Differential Relay with integral four-zone distance backup for easy-to-apply, high-speed line protection.

Apply subcycle current differential protection with included four-zone distance and directional overcurrent backup. Use single or dual differential channels for reliability. Apply the SEL-311L on two- or three-terminal lines. Unique measuring elements provide coordination with tapped loads. Reduce total project construction and operation costs through integration of the included four-shot recloser and relay logic operators into your automation system.

Improve protection system reliability with continuous checks of communications quality, breaker wear, battery voltage, and relay health. Use the included LCD display in place of traditional panel meters.

 

Major Features and Benefits

➤ Synchrophasors. Improve operator awareness of system conditions. Use real-time data to view load angles, improve event analysis, and provide state measurements.

➤ Security and Reliability. Provide security for CT saturation and channel asymmetry by using the Alpha Plane restraint characteristic.

➤ Protection Sensitivity. Provide sensitivity without sacrificing security during external faults through use of negative-sequence current differential and Alpha Plane restraint.

➤ Protection Speed. Subcycle operating times at only four times minimum pickup for phase elements.

➤ Single-Pole Tripping. Improve system stability with optional single-pole tripping by differential and Zone 1 distance elements.

➤ Full-Featured Backup Protection. Standard backup protection includes: four zones of distance protection, directional overcurrent elements, and a four-shot reclose logic system.

➤ Easy to Apply. Select CT ratios and channel ID and the relay is ready to be used on most differential applications. Use application settings for simplifying setting requirements.

➤ Communication Security. True hot standby communications for no loss or degradation in protection during single channel failure. Isolation of 1.5 kV on electronic differential communication circuits.
IEEE C37.94 fiber to multiplexer compatible. Multiple channel paths do not require the same baud rate or channel delay.

➤ Three-Terminal Application. Apply the SEL-311L on three-terminal lines without compromising protection even on loss of a single differential channel.

➤ Mismatched CTs. Set the CT ratio for all connected terminals. The Alpha Plane restraint characteristic prevents misoperation due to mismatched characteristics such as voltage class or burden.

➤ Automation. Equip the SEL-311L with optional dual fail-over Ethernet communications for Telnet, FTP, read-only web server, and IEC 61850 communications support.

 

Functional Overview

- Advanced SELOGIC® Control Equations
- Event Reports With Oscillography
- Sequential Events Recorder
- Breaker Wear Monitor
- Station Battery Monitor
- DNP3 Level 2 Slave Protocol*
- MIRRORED BITS® Communications and Advanced Scheme Logic
- Synchrophasors
- Remote and Local Control Switches
- Local Display
- Fault Locator
- CCVT Transient Overreach
*Optional Function

 

Protection Features

The SEL-311L contains an advanced line current differential system that is easy to set and apply, while still giving subcycle operation and superior fault resistance coverage. It is suitable for protection of any transmission line or underground cable where digital communications, in the form of either a 56/64 kb channel or a dedicated fiber-optic interface is available. Enable as many as four zones of phase and ground mho distance backup elements plus four zones of ground quadrilateral distance elements. These distance elements, together with overcurrent functions, may be applied in communicationsassisted and stepped-distance protection schemes (see Figure 1).

Predefined configurations for typical applications are included in the relay settings. These configurations allow for greatly reduced settings for many line configurations, with or without potential transformers. 

 

Protection Elements

The SEL-311L differential elements compare phase and sequence components from each line terminal, as illustrated in Figure 2. Because line charging current has a very low negative-sequence component, negativesequence current differential protection allows for high sensitivity without compromising security. The phase elements provide high-speed protection for severe or balanced faults. This allows high-speed operation even under heavy load flow conditions when system stability may be critical.

The innovative differential protection in the SEL-311L checks the vector ratio of the local and remote currents in a complex plane, known as the Alpha Plane, as shown in Figure 3, Figure 4, Figure 6, and Figure 7.

For load and external faults, with no CT or communication errors, the vector ratio of remote current to local current will be –1 or 1180º. Errors introduced from CTs or nonequal communications path delays cause the ratio to appear at different locations within the complex ratio plane. The SEL-311L restraint characteristic improves on prior systems. The SEL-311L restraint region surrounds the ideal external fault and load current point allowing for errors in both magnitude and phase angle. CT saturation, channel asymmetry, and other effects during faults outside the protected zone produce shifts in the magnitude and angle of the ratio. The restraint characteristic provides proper restraint for these conditions and still detects high-impedance faults and “outfeed” faults that occur within the protected zone. The restraint region is adjustable both in angular extent and radial reach.

The differential protection algorithms are insensitive to CT saturation effects due to different CT characteristics at the line ends or remnant CT flux. This prevents tripping on through faults and allows the use of existing CTs at each line end. The SEL-311L current connections add very little burden, which allows line current differential protection to be added to multiuse CTs without degradation of accuracy (see Figure 5 and Figure 6).
















 

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