siemens
Siemens SIPROTEC 7UT85 Transformer Differential Protection Relay
Model: 7UT8511-5EB91-0AA0
4-hour response · Pricing in SAR · Delivery across all KSA regions
7UT8511-5EB91-0AA0 — Siemens SIPROTEC 7UT85 Transformer Differential Protection Relay
The Siemens SIPROTEC 7UT85 is the most advanced transformer differential protection IED in the SIPROTEC 5 family, providing comprehensive unit protection for two-, three-, and four-winding power transformers across Saudi Arabia's transmission and industrial power systems. The biased differential algorithm incorporates second and fifth harmonic restraint for inrush blocking, overexcitation restraint, and cross-blocking between phases — distinguishing modern numerical protection from older percentage differential relays that required careful setting to avoid misoperation during energisation. Automatic CT ratio compensation and zero-sequence current elimination handles any transformer vector group without external interposing CTs.
Restricted earth-fault (REF) protection detects high-resistance winding-to-earth faults that the differential algorithm may not see at low fault current levels. On-load tap changer (OLTC) monitoring tracks tap position and counts switching operations for maintenance interval planning. IEC 61850 GOOSE messaging with IEEE 1588 PTP simultaneously intertrips remote HV and LV terminal breakers within 5 ms, rapidly clearing internal faults without sustained infeed from both transformer sides. Overexcitation protection (24) detects abnormal flux density from overvoltage or underfrequency that damages transformer core laminations.
In Saudi Arabia, the 7UT85 is the standard transformer protection relay for SEC and SCECO transmission substations, ARAMCO and SABIC HV/MV substation transformers, large power plant unit transformers, and industrial HV/MV transformers at petrochemical and manufacturing facilities. DIGSI 5 within TIA Portal integrates relay engineering with substation automation from a unified workspace, reducing engineering time on integrated digital substation projects.
Razz Middle East provides complete 7UT85 project services — specification, DIGSI 5 engineering, factory acceptance testing, site commissioning, and IEC 61850 GOOSE configuration — across Saudi Arabia.
Technical Specifications
Full specifications for the 7UT8511-5EB91-0AA0
- Protected Transformers
- 2, 3, and 4-winding
- Differential
- Biased with 2nd and 5th harmonic restraint
- Backup
- REF, 50/51 OC, 24 Overexcitation
- CT Compensation
- Automatic vector group and ratio correction
- Communication
- IEC 61850 Ed2, GOOSE, IEEE 1588 PTP
- OLTC
- Tap position monitoring and counter
- Software
- DIGSI 5
- Standard
- IEC 60255-111
Key Features & Benefits
- Second and fifth harmonic restraint with cross-blocking prevents misoperation during transformer energisation inrush while maintaining sensitivity for genuine internal fault detection.
- Automatic CT ratio compensation and zero-sequence elimination handles any transformer vector group (Dy, Yd, Yy, zigzag) without external interposing CTs or complex manual settings.
- Restricted earth-fault (REF) protection detects high-resistance winding-to-earth faults that biased differential may not see at low fault current levels, providing comprehensive winding earth fault coverage.
- OLTC monitoring tracks tap position and counts switching operations, providing maintenance data for service interval planning before contact wear causes dielectric failure.
- IEC 61850 GOOSE with IEEE 1588 PTP simultaneously intertrips HV and LV terminal breakers within 5 ms, rapidly clearing internal faults without sustained infeed from both transformer sides.
- Overexcitation protection (24) detects abnormal flux density from overvoltage or underfrequency — the slowly developing failure mode damaging transformer core laminations not covered by differential protection.
- DIGSI 5 within TIA Portal integrates transformer relay engineering with substation automation in a single tool, reducing project engineering time and tool licensing cost.
Industrial Applications in Saudi Arabia
- SEC transmission substation power transformer protection at 115 kV/33 kV and 33 kV/13.8 kV substations throughout the Kingdom, where harmonic restraint prevents misoperation during transformer energisation switching.
- ARAMCO refinery HV/MV unit substation transformer protection, where GOOSE intertripping with SIPROTEC 7SJ82 feeder relays provides fast selective fault isolation.
- SABIC Jubail petrochemical complex HV substation transformer protection, where OLTC monitoring tracks tap changer condition for planned maintenance before in-service failure.
- Power plant unit and generator transformer protection at Saudi IPPs and cogeneration facilities, protecting the critical generator step-up transformer.
- NEOM and Red Sea Project primary substation transformer protection, where IEEE 1588 and IEC 61850 provide interoperability with the digital substation platform.
- Large industrial HV/MV transformers at cement, steel, and mining facilities, where REF protection covers high-resistance winding earth faults the biased differential may not detect.
- Autotransformer protection at SEC interconnection substations, where the 7UT85's three-winding mode covers complex current distribution across common and series windings.
Industrial Supplier in Saudi Arabia
Get a Quote for the Siemens SIPROTEC 7UT85 Transformer Differential Protection Relay
We respond within 4 business hours. Send model 7UT8511-5EB91-0AA0 for competitive pricing in SAR with delivery across Saudi Arabia and the GCC.
Frequently Asked Questions — 7UT8511-5EB91-0AA0
Common questions from buyers in Saudi Arabia and the GCC