Siemens Siprotec 5 7UT87 Transformer Differential Protection Relays

The SIPROTEC 7UT87 transformer different,ial protection has been designed specifically for the protection of multi-winding transformers (up to 5 sides). Furthermore, it is to be used where numerous measuring points (up to 9 3-phase current measuring points) are required. Another application is simultaneous protection of two parallel transformers (additional fast backup protection). The SIPROTEC 7UT87 is the main protection for the trans- former and contains many other protection and monitoring functions. The additional protection functions can also be used as backup protection for subsequent protected objects (such as cables or lines). With its modular structure, flexibility, and the powerful DIGSI 5 engineering tool, SIPROTEC 7UT87 offers future-oriented system solutions. Moreover, with high investment security and low operating costs.

7UT87 Transformer Differential Protection Relay Features

Main function:

• Up to 3 differential protection functions with additional stabilization (in different transformer function groups); up to 5 ground fault differential protection functions.
• For auto transformer applications, two differential protection functions can be processed in an Auto transformer function group.
• Interoperability of SIPROTEC 5 and SIPROTEC 4 line protection devices

Usable measuring points:

• 9 x 3-phase current measuring points,
• 5 x 1- phase current measuring points,
• 5 x 3-phase voltage measuring points

Inputs and outputs:

2 predefined standard variants with

• 20 current transformers,
• 4 voltage transformers,
• 15 to 27 binary inputs,
• 22 to 38 binary outputs

Hardware flexibility:

• Flexibly adjustable and expandable I/O quantity structure within the scope of the SIPROTEC 5 modular system.

Width of housing:

• 2/3 × 19 inches to 2/1 × 19 inches

As standard:

• Conformal coating

Functions

DIGSI 5 permits all functions to be configured and combined as required. In SIPROTEC 7UT87, two transformer function groups can be used.

• Provides transformer differential protection for multi-winding transformers used in applications such as HVDC power converters.

• Supports protection for phase-angle regulating transformers, including single-core and two-core types, as well as special transformers.

• Allows up to seven three-phase current measuring points, enabling advanced transformer monitoring.

• Enables simultaneous differential protection for two transformers, such as two separate two-winding transformers.

• Offers flexible use of measuring points, allowing easy configuration for different transformer designs.

• Suitable for medium-, high-, and extra-high-voltage transformer protection.

• Protects standard power transformers, autotransformers, and large motors.

• Includes key differential protection features such as vector-group adaptation, inrush current blocking, and overexcitation control.

• Maintains stable operation during current-transformer saturation, even with varying saturation levels.

• Provides Fault Locator Plus for precise fault location, even on inhomogeneous line sections.

• Supports arc protection for improved system safety.

• Includes voltage controller function (ANSI 90V) for two-winding, three-winding, and grid-coupling transformers with parallel control.

• Adapts the operate curve automatically based on transformer tap position.

• Improves sensitivity for near-neutral-point ground faults through restricted ground-fault protection.

• Supports point-on-wave switching to reduce switching stress on equipment.

• Allows additional current and voltage inputs for protection functions such as overcurrent, voltage, and frequency protection.

• Features a graphical logic editor to build advanced automation functions within the device.

• Supports up to four pluggable communication modules for protocols including IEC 61850, IEC 60870-5-103/104, Modbus TCP, DNP3, and PROFINET IO.

• Ensures reliable communication through PRP and HSR redundancy protocols.

• Provides advanced cybersecurity features, including role-based access control and security event logging.

• Enables secure web-browser access to device data without additional software.

• Supports secure serial communication over optical fiber, two-wire links, and communication networks.

• Captures operational measurements and protection data to support system evaluation and fault analysis.

• Offers frequency-tracked protection functions from 10 Hz to 80 Hz with multiple tracking groups.

Applications

The SIPROTEC 7UT87 is intended for special applications (up to 5 sides and 7 measuring points), therefore, you must create your own application template depending on the application and store it in the device. To make work easier, you can use an available template and modify it.

Example:

Auto transformer with stabilizing winding in breaker-and-a-half layout

• Differential protection for the complete transformer (auto transformer winding + stabilizing winding)
• Nodal point protection for the auto winding for recording ground faults (3-phase recording of the neutral-point current)
• Overload protection, backup protection for the downstream power system
• Circuit-breaker failure protection
• Frequency and voltage protection on the upper-voltage side.

Line protection

• Line differential protection
• Serial protection communication with SIPROTEC 5 and SIPROTEC 4 devices over different distances and physical media, such as optical fiber, two-wire connections, and communication networks

SIPROTEC 5 is part of the new generation of incomparable modular, flexible, and intelligent digital field devices. With modularly designed hardware and software and its high-performance DIGSI 5 engineering tool, the SIPROTEC 5 product family of field devices are perfect for protection, control, monitoring, and measuring applications in electrical energy systems. SIPROTEC 5 offers a wide product range with modular elements for every application and requirement.