English
简体中文
News
Get to know our latest news
ABB Protection Relay REX 521 Technical Reference Manual, General
Source: | Author:kongjiang | Published time: 2026-10-18 | 25 Views | 🔊 Click to read aloud ❚❚ ▶ | Share:
ABB Protection Relay REX 521 Technical Reference Manual, General

ABB Protection Relay REX 521 

Technical Reference Manual, General

Safety information
Dangerous voltages can occur on the connectors, even though the auxiliary voltage has been disconnected.
Non-observance can result in death, personal injury or
substantial property damage.
Only a competent electrician is allowed to carry out the electrical installation.
National and local electrical safety regulations must always be followed.
The frame of the device has to be carefully earthed.
The device contains components which are sensitive to electrostatic discharge. Unnecessary touching of electronic components must therefore be avoided.

Breaking the sealing tape on the rear panel of the device will result in loss of warranty and proper operation will no longer be guaranteed.

Introduction
General
The protection relay REX 521 is designed for protection, control, measuring, and supervision in medium voltage networks. Typical applications include incoming and outgoing feeders as well as substation protection. The protection relay is provided with energizing inputs for conventional current and voltage transformers. Also, a hardware version with inputs for current and voltage sensors is available.
The protection relay is based on a multiprocessor environment. The HMI1 (Human Machine Interface), including an LCD (Liquid Crystal Display) with different views, makes local use easy and informs the user via indication messages. Modern technology is applied in both hardware and software solutions.
The REX 521 is part of the substation automation concept for Distribution Automation and extends the functionality and flexibility of the concept further.
REX 521 Protection Relay
Technical Reference Manual, General
Application
•The REX 521 is designed for protection of incoming and outgoing feeders in medium voltage distribution substations. Further, the relay can, for example, be applied to back-up protection of power transformers and back-up for high voltage line protection relays.
Protection Relay REX 521
Technical Reference Manual, General
Requirements
If the environmental conditions differ from those specified in section “Technical data” on page 48, as to temperature and humidity, or if the environmental conditions around the protection relay contain chemically active gases or dust, the relay should be visually inspected in association with the secondary testing. The visual inspection should focus on:
• Signs of mechanical damage to the relay case and terminals.
• Signs of corrosion on terminals or on the case.
• For information about the maintenance of relays, refer to section “Service” on page 59.
Protection relays are measuring instruments and should be handled with care and protected against moisture and mechanical stress, especially during transport.
REX 521 Technical Reference Manual, General
Non-volatile memory
The protection relay is equipped with a non-volatile memory for preserving
important data during auxiliary supply breaks. For example, when a setting value is
changed, the new value is stored in the memory at the moment of sending it to the
relay, without additional store commands. The memory does not need batteries, and
a lifelong service is guaranteed.
The following data is stored in the non-volatile memory:
• Setting values
• Display state
• Lockout state
• Recorded values1
• Last 50 events
When the relay is restarted, the LED indication and text displayed before the auxiliary supply break are restored on the display. More information about the alarm LEDs can be found in section “Alarm LEDs” on page 45.
Recorded values are stored from start, trip, and other important events. After an auxiliary power break, time and date and fault currents for the three last events can be viewed by navigating to the “Recorded values” section of the function block that caused an indication.
The last 50 events that occurred before the auxiliary power supply break can be viewed in the HMI event buffer. Time and date for the events are also restored.
Real-time clock
The real-time clock (RTC) is used for time stamping of events. It is also running during auxiliary power breaks. When the supply is re-established, the relay sets the correct time and new events are stamped accordingly.
The protection relay is provided with a 1-week capacitor back-up protection that enables the internal clock to keep time in case of an auxiliary power failure.
Auxiliary voltage
For its operation, the protection relay requires a secured auxiliary voltage supply. The protection relay’s internal power supply module forms the voltages required by the protection relay electronics. The power supply module is a galvanically isolated (flyback-type) DC/DC converter. A green LED indicator on the front panel is lit when the power supply module is in operation.
Power supply versions
There are two basic versions of power supply modules available for REX 521 protection relays: type PS_87H and type PS_87L.
The input voltage range of the power supply module is marked on the front panel of the REX 521 unit. The power supply version is specified by a letter in the order number of the protection relay (refer to section “Ordering information” on page 61).
The voltage range of the digital inputs is tied to the selected power supply. If a power supply version with the higher rated input voltage is selected, the protection relays will be delivered with digital inputs that also have the higher rated input voltage. The digital input, DI9, on the CPU module has a lower rated input voltage.
The auxiliary voltages of power supply modules and the corresponding rated input voltages of digital inputs are:
Low auxiliary voltage indication
The relay is provided with a low auxiliary voltage indication feature. The power supply module issues an internal alarm signal when a drop in the power supply voltage is detected. The alarm signal is activated if the power supply voltage falls about 10% below the lowest rated DC input voltage of the power supply module; see the following table:
• Rated input voltage 110/125/ 220 V DC
• Rated input voltage 110/120/220/ 240 V AC
PS_87L
• Rated input voltage 24/48/60 V DC
Overtemperature indication
The REX protection relay includes an internal temperature supervision function. The CPU module issues an internal alarm signal when overtemperature has been detected inside the relay enclosure. The alarm signal will be activated once the temperature inside the relay enclosure increases approximately to +78oC. The overtemperature indication can be seen on the HMI or as an event via serial communication. The relay will go to the IRF (internal relay fault) state. See Table 5.1.11.2-1, “Fault indications,” on page 35.
Scaling the rated values of the protected unit for analog
channels
A separate scaling factor can be set for each analog channel. The factors enable differences between the ratings of the protected unit and those of the measuring device (CTs, VTs, etc.) The setting value 1.00 means that the rated value of the protected unit is exactly the same as that of the measuring device.
When scaling factors are used, it should be noted that they affect the operation accuracy of the relay. The accuracies stated in the description of each function block (in the CD-ROM Technical Descriptions of Functions) only apply with the default values of the scaling factors. For example, a high factor affects the operation of sensitive protection functions such as the directional earth fault protection. To ensure the proper operation of the function blocks, it must be checked that the analog scales (pu scales) of the phase currents IL1, IL2, and IL3, and correspondingly, the analog scales of the phase-to-phase voltages U12, U23, and U31 or phase-to-earth voltages U1, U2, and U3 are identical.
The scaling factors for the analog channels can be set via the HMI of the protection relay or with the Relay Setting Tool. The HMI path for the scaling factors is: ConfigurationProtected unitIL1: scaling, IL2: scaling...
Technical data of the measuring devices
The technical data of the measuring devices is set using the Relay Setting Tool or via HMI. The set values (ConfigurationMeas.devices) will affect the measurements carried out by REX 521.
Values to be set for a current transformer:
• rated primary current (1...6000 A) of the current transformer
• rated secondary current (5 A, 2 A, 1 A, 0.2 A) of the current transformer
• rated current (5 A, 1 A, 0.2 A) of the current measuring input (= rated current of the matching transformer of the protection relay)
• amplitude correction factor (0.9000...1.1000) of the current transformer at rated current
• correction parameter for the phase displacement error of the current transformer at rated current (-5.00°...0.00°)
• amplitude correction factor of the current transformer at a signal level of 1% of the rated current (0.9000...1.1000)
• correction parameter for the phase displacement error of the current transformer at a signal level of 1% of the rated current (-10.00°...0.00°)
Values to be set for a voltage transformer:
• rated voltage of primary voltage transformer (0.100...440.000 kV)
• rated voltage of voltage input (same as the secondary rated voltage of the primary voltage transformer connected to the voltage input, 100 V, 110 V, 115 V, 120 V)
• amplitude correction factor of the primary voltage transformer voltage at rated voltage (0.9000...1.1000)
• correction parameter for the primary transformer phase displacement error at rated voltage (-2.00°...2.00°)
Values to be set for a current sensor (Rogowski coil):
• secondary rated voltage of the current sensor used at the preset primary rated current (100...300 mV)
• primary rated current of the current sensor used (1...6000 A) • amplitude correction factor of the current sensor used at rated current (0.9000...1.1000)
• correction parameter for the phase displacement error of the current sensor (-1.0000°...1.0000°)
Principle of the protection functions mapping
The REX 521 applications, whose modularization is based on trip stages, have been mapped into the IEC 60870-5-103 information numbers according to the following model:
Class 2 data
The measurement (analog) values are transported to the control system as a response to a class 2 request command. The class 2 data is always cyclically updated (COT=2). See Table 9.5.-3 on page 71 for measurement data.
Class 2 measurand sets (ASDU frames)
The IEC 60870-5-103 standard defines the measurands to be transmitted as either Meas I (typeId 3) or Meas II (typeId 9) ASDU frames. According to the standard, the Meas I ASDU can have four different profiles, and Meas II has one profile. These five profiles are supported in REX 521. In addition, there are six more private class 2 ASDU frames defined. The user can choose which one of these eleven measurand sets to use. The measurand set number (1...11) can be adjusted via the Frame type parameter.
Class 2 value scaling
The IEC 60870-5-103 standard defines the scale (max. range) of the measurements to be either 1.2 or 2.4 times the rated value for the measurement. The selection between the 1.2 scaling and the 2.4 scaling can be done via the Scale factor parameter. In order for the analog (measurement) data to become available on the IEC 60870-5-103 interface, the measurement applications must have the measurement threshold with a proper threshold value selected.