The NOVA NX-STS recloser is a single-tank, triple-single, electronically controlled recloser designed for overhead distribution systems. It provides automatic circuit interruption and reclosing to restore power after temporary faults, and isolates permanent faults to minimize outage time. The recloser is available in 15 kV, 27 kV, and 38 kV voltage ratings, with various current ratings and short-circuit interrupting capabilities.
Function Description
The NOVA NX-STS recloser is comprised of three single-phase reclosers in a single tank. Each recloser utilizes an interrupting module, a current transformer, and a medium connected to an aluminum head casting. The three-phase polymer tank enclosure is suitable for pole or substation mounting and is corrosion resistant. The interrupter modules utilize outdoor cycloaliphatic-epoxy-encapsulated vacuum interrupters. The NOVA NX-STS recloser is controlled by a single microprocessor-based recloser control that can be programmed for three operating modes: single-phase trip, single-phase lockout; single-phase trip, three-phase lockout; and three-phase trip, three-phase lockout.
The recloser's primary function is to detect and interrupt fault currents, then automatically reclose to restore power if the fault is temporary. If the fault persists, the recloser will perform a programmed sequence of operations (trip and reclose attempts) before finally locking out, isolating the faulted section of the circuit. This minimizes the impact of faults on the overall distribution system.
Important Technical Specifications
The NOVA NX-STS recloser is available in three voltage ratings: 15 kV, 27 kV, and 38 kV.
- 15 kV Recloser:
- Rated maximum voltage: 14.4 kV (rms)
- Nominal system voltage: 12.5 kV (rms)
- Rated short-duration power-frequency withstand voltage: 50 kV (rms)
- Rated lightning impulse withstand voltage: 110 kV (peak)
- Rated continuous current: 630 A
- Rated short-time withstand current (kA peak): 32.5 kA
- Rated peak withstand current (kA peak): 41.6 kA
- Rated duration of short-circuit: 3 seconds
- Rated short-circuit breaking current (kA, sym): 12.5 kA
- Rated symmetrical short-circuit making current (kA, sym): 32.5 kA
- Rated cable charging interrupting current: 10 A
- Rated cable charging interrupting current (A): 10 A
- Minimum mechanical operations without maintenance: 10,000
- Mass (weight) – kg (lb): 161 (354) with pole-mounting frame
- 27 kV Recloser:
- Rated maximum voltage: 27.0 kV (rms)
- Nominal system voltage: 24.9 kV (rms)
- Rated short-duration power-frequency withstand voltage: 60 kV (rms)
- Rated lightning impulse withstand voltage: 125 kV (peak)
- Rated continuous current: 630 A
- Rated short-time withstand current (kA peak): 32.5 kA
- Rated peak withstand current (kA peak): 41.6 kA
- Rated duration of short-circuit: 3 seconds
- Rated short-circuit breaking current (kA, sym): 12.5 kA
- Rated symmetrical short-circuit making current (kA, sym): 32.5 kA
- Rated cable charging interrupting current: 10 A
- Rated cable charging interrupting current (A): 10 A
- Minimum mechanical operations without maintenance: 10,000
- Mass (weight) – kg (lb): 165 (363) with pole-mounting frame
- 38 kV Recloser:
- Rated maximum voltage: 38.0 kV (rms)
- Nominal system voltage: 34.5 kV (rms)
- Rated short-duration power-frequency withstand voltage: 70 kV (rms)
- Rated lightning impulse withstand voltage: 170 kV (peak)
- Rated continuous current: 630 A
- Rated short-time withstand current (kA peak): 32.5 kA
- Rated peak withstand current (kA peak): 41.6 kA
- Rated duration of short-circuit: 3 seconds
- Rated short-circuit breaking current (kA, sym): 12.5 kA
- Rated symmetrical short-circuit making current (kA, sym): 32.5 kA
- Rated cable charging interrupting current: 10 A
- Rated cable charging interrupting current (A): 10 A
- Minimum mechanical operations without maintenance: 10,000
- Mass (weight) – kg (lb): 170 (374) with pole-mounting frame
The recloser meets IEEE Std C37.60™–2018, IEEE Std C37.90.1™–2012, and IEEE Std C37.90.2™–2004 standards, and is ISO® 9001 Certified Quality Management System compliant.
Usage Features
- Electronic Control: The recloser is operated via a microprocessor-based control unit that allows for programmable operating sequences, including trip and reclose attempts, time delays, and lockout settings. This control unit is typically mounted separately from the recloser itself.
- Operating Handle: A yellow manual operating handle is provided for local operation. Pushing the handle down opens the recloser, and pulling it up closes it. This handle also serves as a visual indicator of the recloser's open or closed status.
- Contact Position Indicator: A mechanical indicator shows the open or closed status of the recloser contacts, providing a visual confirmation of the recloser's state.
- Lockout Indicator: A red indicator flag appears when the recloser is in a lockout condition, signifying that it will not reclose automatically until manually reset.
- Integrated Voltage Sensing Option (6 sensors): The recloser can be equipped with integrated voltage sensors for source and load-side voltage sensing. This feature enhances the recloser's ability to perform advanced protection functions and provides valuable system data. The voltage sensors are encapsulated in silicone rubber insulation and connected to the recloser’s load-side terminals.
- Auxiliary Switch: An optional auxiliary switch provides remote indication of the recloser’s open or closed status, allowing for integration into SCADA or other control systems.
- Terminal Options: Various terminal options are available, including eyebolt, flat-pad, and stud type, to accommodate different conductor sizes and connection methods.
- Mounting Hanger: The recloser is designed for pole-mounting, with provisions for mounting brackets to secure it to a utility pole.
- Arrester Mounting Brackets: Optional brackets are available for mounting surge arresters directly to the recloser, providing integrated overvoltage protection.
- Wildlife Guarding: An optional accessory that can be ordered for the NOVA NX-STS recloser is wildlife protection. This unique vented design allows water to easily drain through the wildlife guard and provides visibility to the terminal connection located within the wildlife guard.
Maintenance Features
- Frequency of Inspection: Based on design and operating conditions, visual inspections are recommended every 10 years. However, in areas with severe environmental conditions or high operating experience, more frequent inspections may be necessary. Vacuum interrupters should be inspected every 10 years.
- High-Potential Withstand Tests: The recloser is designed to undergo high-potential withstand tests to verify the dielectric integrity of the recloser. These tests are performed at the factory and can be repeated in the field as part of routine maintenance.
- Troubleshooting: The manual provides detailed troubleshooting procedures for common issues, including module flashover, control unit malfunctions, and wiring problems.
- Module Flashover Service: Procedures are outlined for bypassing and removing the recloser from service, checking dielectric strength, inspecting housing and lifting lugs, and repairing damage to terminals or module rods.
- Easy Access to Components: The design allows for relatively easy access to internal components for inspection and maintenance.
- Documentation: Comprehensive documentation, including wiring diagrams and connection diagrams, is provided to assist with installation, operation, and maintenance.
- Factory Support: Eaton provides factory support and service information to assist with any maintenance or repair needs.
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