Description
Product Introduction
When a power transformer has three winding connections, protection settings and current-transformer inputs must reflect the actual transformer arrangement. The GE Multilin SR745-W3-P5-G5-HI is a three-winding transformer protection relay intended for applications that require coordinated protection and monitoring across multiple transformer sides.
Its configuration specifies 5 A phase and ground current inputs and high-range control power. When sourcing this GE 745 relay, confirm the complete nameplate, auxiliary supply, CT wiring, firmware, and existing protection settings before treating it as a direct replacement for an installed unit.
Key Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | GE Multilin |
| Model | SR745-W3-P5-G5-HI |
| Relay family | 745 Transformer Protection System |
| Winding configuration | W3 — three windings per phase |
| Phase CT rating | P5 — 5 A for all applicable windings |
| Ground CT rating | G5 — 5 A for the specified winding pairs |
| Auxiliary power, DC | 90–300 VDC |
| Auxiliary power, AC | 70–265 VAC, 48–62 Hz |
| Core application | Transformer protection and management |
| Differential protection | Supported by the 745 platform; verify settings and enabled functions |
| Display | Confirm actual fitted display option |
| Analog I/O | Not indicated by the supplied code; confirm if required |
| Loss-of-life monitoring | Not indicated by the supplied code |
| Restricted ground fault | Not indicated by the supplied code |
| Ethernet | Not indicated by the supplied code |
| Installation | Panel-mounted SR-family relay; verify case and wiring arrangement |
| Operating temperature | Consult the applicable GE instruction manual |
The HI suffix identifies the high-range auxiliary power option. The absence of A, L, R, E, or T in the supplied code means those options should not be assumed to be installed. GE distinguishes enhanced display (E) from enhanced display plus 10Base-T Ethernet (T).
SR745-W3-P5-G5-HI
Application Scenarios & Pain Points
The key replacement challenge is matching the relay to the transformer and the existing protection scheme, not simply matching the front-panel model family.
- Three-winding power transformers: Use the correct winding configuration and CT input ratings for each transformer side.
- Substation protection upgrades: Verify differential protection settings, restraint characteristics, and trip logic against the approved scheme.
- Industrial power distribution: Confirm the relay’s auxiliary supply and output-contact requirements before connecting control circuits.
- Legacy relay maintenance: Preserve the original settings and event records where possible, then verify hardware and firmware compatibility.
Field note: a relay may power up normally while still having incorrect CT ratios, polarity, or protection settings. Validate those items during commissioning before returning the transformer to service.
Related Products
These models belong to the GE Multilin 745 family or represent nearby configuration variants. They are not automatically interchangeable.
- 745-W3-P5-G5-HI-R-E — Three-winding, 5 A phase/ground input version with restricted ground-fault protection and enhanced display.
- 745-W3-P5-G5-HI-A — Three-winding version with analog inputs/outputs.
- 745-W3-P5-G5-HI-A-L-R-E — Three-winding version with analog I/O, loss-of-life monitoring, restricted ground fault, and enhanced display.
- 745-W2-P5-G5-HI — Two-winding configuration; winding arrangement differs from the target model.
- 745-W3-P1-G1-HI — Three-winding version with 1 A phase and ground current inputs; CT interface differs from the target model.
GE’s ordering table defines the differences between these configuration fields. Confirm the exact installed options before selecting a replacement.
Engineer’s Guide: Three Replacement Checks
1. Confirm all three CT interfaces. The W3-P5 code indicates a three-winding configuration with 5 A phase-current inputs. Verify CT secondary ratings, polarity, ratios, and wiring against the approved drawings.
2. Check the high-range auxiliary supply. The HI version is specified for 90–300 VDC or 70–265 VAC at 48–62 Hz. Verify the available supply and the relay nameplate before energizing the unit.
3. Validate options and protection settings. Do not assume analog I/O, loss-of-life monitoring, restricted ground-fault protection, or Ethernet is present. Confirm the installed hardware and settings, then test protection elements, alarms, outputs, and trip paths under the site’s approved commissioning procedure.
Frequently Asked Questions
What is the GE SR745-W3-P5-G5-HI used for?
It is a GE Multilin 745 transformer protection relay configured for three windings per phase. The 745 family supports transformer protection and management functions for utility and industrial power systems.
What does W3-P5-G5 mean?
W3 indicates three windings per phase. P5 specifies 5 A phase-current inputs for the applicable windings, while G5 specifies 5 A ground-current inputs for the relevant winding pairs.
What is the power supply range?
The HI configuration supports 90–300 VDC or 70–265 VAC at 48–62 Hz. Confirm the exact unit’s label and supply requirements before connecting power.
Does this model include Ethernet or analog I/O?
Those options are not indicated in the supplied model string. GE identifies A with analog inputs/outputs, E with enhanced display, and T with enhanced display plus Ethernet. Check the complete nameplate before assuming any optional function is available.
Can I replace it with a two-winding 745 relay?
Not as a direct substitution without a formal engineering review. The W2 and W3 configurations address different transformer winding arrangements, and the CT inputs, settings, wiring, and protection scheme must match the actual installation.
How should I verify a used or refurbished unit?
Request photographs of the complete nameplate, terminal side, and fitted modules. Ask for a functional test report, a clear condition description, and written warranty terms. For a protection relay, a power-on check alone does not prove that the differential and trip functions operate correctly.
What information should I provide for a quotation?
Send the complete model number, photographs of the installed relay, transformer winding configuration, CT secondary ratings, required condition, and delivery deadline. Request confirmation of the exact option configuration, stock status, test scope, warranty, and lead time.
Procurement recommendation: The critical checks for the SR745-W3-P5-G5-HI are its three-winding configuration, 5 A CT inputs, and high-range auxiliary supply. Confirm those against the existing relay and approved protection drawings before ordering.
