Product Overview
Functional Definition
The ZWJ-12 series high-voltage prepaid metering boxes are integrated load control and metering devices designed for 10 kV, 50 Hz power distribution systems with capacity up to 5000 kVA. These modular units combine vacuum circuit breaker (VCB), voltage transformer (PT), and current transformer (CT) in a fully enclosed configuration to provide energy metering, prepaid management, load control, overcurrent protection, and anti-theft functionality.
Key Ratings
| Item | Specification (per order / nameplate) |
|---|---|
| System voltage class | 12 kV (10 kV rated voltage application) |
| Rated frequency | 50 Hz |
| Rated capacity | Up to 5000 kVA |
| Control circuit voltage | AC 220 V ±10% |
| CT secondary current | 5 A |
| PT secondary voltage | 0.1 kV / 0.22 kV (dual secondary) |
| CT accuracy class | 0.2S class (10 VA burden) |
| PT accuracy classes | 0.2 class (20 VA) / 3P class (50 VA) |
| Rated breaking current (peak) | 50 kA |
| Short-time withstand current | 20 kA (4 s) |
| Peak withstand current | 50 kA |
| Circuit breaker type | ZW8-12 vacuum circuit breaker |
| Applicable standards | GB 17201-2007; GB 1984-2003; IEC 61869-1 / IEC 61869-2; GB/T 20840 series |
Product Variants
- ZWJ-12 / ZWJ-12GY: Standard prepaid metering box with integrated VCB, PT, and CT. Modular design with upper chamber for circuit breaker and lower chamber for instrument transformers. Available in integrated or separated installation configurations.
- ZWJ-12F: Remote metering and management type with fault location, rapid fault recovery, remote communication, and intelligent control. Suitable for urban, rural, and agricultural power supply applications.
- ZWJ-12LD: Rural grid retrofit type featuring prepaid metering, composite metering functions, current limiting, short-circuit protection, and overvoltage protection. Outdoor-rated for substation, commercial, and rural distribution applications.
- ZWJ-12/Z3: Integrated VCB-PT-CT metering box with fully enclosed epoxy resin structure for enhanced insulation performance.
Working Principle
The ZWJ-12 series integrates vacuum circuit breaker switching, instrument transformer measurement, and prepaid control in a single unit. The vacuum circuit breaker provides load switching and fault interruption. Current transformers convert primary current to standardized 5 A secondary output for metering and protection. Voltage transformers provide dual secondary outputs (0.1 kV and 0.22 kV) for metering circuits and auxiliary systems. The integrated three-phase electronic meter enables prepaid management, remote monitoring, automatic billing, and load disconnection when credit is exhausted.
System Application Position
- Urban Distribution Networks: 10 kV overhead lines and cable distribution systems
- Rural Electrification: Village and agricultural power supply networks
- Commercial Facilities: Shopping centers, office buildings, and industrial parks
- Substation Feeders: Distribution transformer secondary metering and control
- Prepaid Metering Systems: Revenue control applications requiring advance payment
Structural Overview
Fully enclosed stainless steel enclosure with modular internal arrangement. Upper chamber houses ZW8-12 vacuum circuit breaker with manual/motorized operating mechanism. Lower chamber contains epoxy resin cast instrument transformers (PT and CT) with standardized terminal blocks. Lockable access panels with specialized keys prevent unauthorized access and tampering. Integrated base plate simplifies installation without external support structures. Outdoor-rated construction with corrosion-resistant finish suitable for harsh environmental conditions.
Model Designation
Model Code Explanation
- Z — Integrated (combined) structure
- W — Outdoor pole-mounted application
- J — Metering function
- 12 — Maximum voltage class (kV)
- /Z3 — Configuration code (VCB + PT + CT integrated)
- F / LD / GY — Functional variant suffix (remote management / rural grid / standard)
Configuration Features
- Vacuum Circuit Breaker: ZW8-12 type with simplified structure, flexible operation, long service life, and integrated switching-metering functionality
- Intelligent Control Module: Optional GSM communication module for remote communication, meter reading, and control
- Prepaid Management: Three-phase electronic meter with remote monitoring, automatic billing, and credit-based disconnection
- Current Limiting Protection: Maintains safe operation even during power interruption
- Instrument Transformers: Epoxy resin cast construction with superior insulation properties
- Enclosure: Fully enclosed stainless steel with corrosion protection and outdoor rating
Service Conditions
The ZWJ-12 series is designed for outdoor installation in medium-voltage power distribution systems under the following environmental conditions:
Installation Environments
- Ambient temperature: -40°C to +55°C (daily variation not exceeding 25°C)
- Extreme temperature range: -45°C to +60°C
- Altitude: ≤ 2000 m above sea level
- Seismic capability: Earthquake intensity ≤ 8 degrees
- Wind pressure: ≤ 700 Pa (wind speed ≤ 34 m/s)
- Relative humidity: No condensation under normal operating conditions
- Pollution degree: Class III per IEC 60664-1
- Ice coating thickness: ≤ 10 mm
- Installation location: Free from fire hazard, explosion risk, severe corrosion, or violent vibration
Construction
Construction Design
- Enclosure: Fully enclosed outdoor-rated stainless steel cabinet
- Upper chamber: Vacuum circuit breaker with operating mechanism
- Lower chamber: Epoxy resin cast instrument transformers (PT and CT)
- Base plate: Integrated mounting platform for all components
- Insulation system: Epoxy resin casting for PT and CT windings
- Access panels: Lockable doors with specialized key system
- Terminal arrangement: Standardized terminal blocks for external connections
Windings & Terminal Marking
Current Transformer (CT) Terminals:
- Primary terminals: P1 (line side) / P2 (load side)
- Secondary terminals: K1 / K2 (standardized 5 A output)
Voltage Transformer (PT) Terminals:
- Primary terminals: A / X (10 kV)
- Secondary terminals (metering): a / x (0.1 kV, 20 VA, 0.2 class)
- Secondary terminals (auxiliary): aⁿ / xⁿ (0.22 kV, 50 VA, 3P class)
Terminal markings follow standard instrument transformer polarity conventions per IEC 61869 and GB/T 20840 series. Correct terminal identification and polarity shall be verified during installation to ensure accurate metering and proper protection operation.
Technical Data
Data Reference
Circuit Breaker Performance Parameters:
| Parameter | Value |
|---|---|
| Maximum voltage | 12 kV |
| Rated load capacity | 5000 kVA |
| Rated breaking current (peak) | 50 kA |
| Rated short-time withstand duration | 4 s |
| Rated short-time withstand current | 20 kA |
| Rated peak withstand current | 50 kA |
| Control circuit voltage | AC 220 V ±10% |
| Average opening speed | 1.1 ± 0.2 m/s |
| Average closing speed | 0.8 ± 0.2 m/s |
| Closing time | ≤ 60 ms |
| Opening time | ≤ 60 ms |
Instrument Transformer Specifications:
| Transformer Type |
Ratio | Rated Burden & Accuracy Class |
|---|---|---|
| Voltage Transformer (PT) | 10 kV : 0.1 kV : 0.22 kV | 10:0.1 kV — 20 VA, 0.2 class 10:0.22 kV — 50 VA, 3P class |
| Current Transformer (CT) | 300 (150) : 5 A | 10 VA, 0.2S class |
| 200 (100) : 5 A | ||
| 150 (75) : 5 A | ||
| 100 (50) : 5 A | ||
| 50 (25) : 5 A | ||
| 30 (15) : 5 A | ||
| 10 (5) : 5 A |
Standards & Normative References
The ZWJ-12 series metering boxes are designed, manufactured, and tested in accordance with the following standards:
- GB 17201-2007: Combined Instrument Transformers
- GB 1984-2003: High-Voltage AC Circuit Breakers
- IEC 61869-1: Instrument Transformers — Part 1: General Requirements
- IEC 61869-2: Instrument Transformers — Part 2: Additional Requirements for Current Transformers
- IEC 61869-3: Instrument Transformers — Part 3: Additional Requirements for Inductive Voltage Transformers
- GB/T 20840.1: Instrument Transformers — Part 1: General Requirements (Chinese equivalent to IEC 61869-1)
- GB/T 20840.2: Instrument Transformers — Part 2: Additional Requirements for Current Transformers
- GB/T 20840.3: Instrument Transformers — Part 3: Additional Requirements for Inductive Voltage Transformers
Factory Test Compliance
Each manufactured unit undergoes routine testing per applicable standards before shipment:
- Vacuum circuit breaker tests: Contact resistance, insulation resistance, mechanical operation sequence, and withstand voltage tests
- Current transformer tests: Ratio verification, polarity check, accuracy class verification at rated burden, insulation resistance, and power frequency withstand voltage
- Voltage transformer tests: Ratio verification, polarity check, accuracy class verification at rated burden, insulation resistance, and power frequency withstand voltage
- Integrated assembly tests: Overall insulation resistance, functional interlock verification, and complete system operation check
- Visual and dimensional inspection: Nameplate marking, terminal identification, and workmanship conformity
Installation & Dimensions
Installation Requirements
- Pre-installation inspection: Verify polarity and accuracy of instrument transformers before installation. Conduct insulation resistance tests.
- Terminal connection: P1 terminal is line side (incoming), P2 terminal is load side (outgoing). Verify proper grounding connection.
- Connection reliability: All terminal connections shall be tight and secure before energization. Verify adequate clearance distances for outdoor service.
- Mounting: Unit shall be securely mounted on supporting structure using designated mounting holes. Ensure level installation.
- Grounding: Connect grounding terminal to station ground grid per local electrical safety codes. Ground resistance shall meet system requirements.
Installation and Maintenance
Key Components and Connections:
Safety Notes
- CT secondary circuit: Do not open CT secondary circuit when primary is energized. Short-circuit and ground secondary before disconnecting meters or relays.
- PT secondary circuit: Do not leave PT secondary terminals floating when primary is energized. Maintain proper fusing in secondary circuits.
- Maintenance procedures: De-energize and verify zero voltage before performing any maintenance work. Follow lockout-tagout procedures.
- Periodic maintenance: Regularly clean enclosure surfaces and inspect sealing integrity. Verify mechanical operation of circuit breaker and prepaid control system.
For special configurations, non-standard ratios, extreme environmental conditions, or custom enclosure requirements, technical confirmation shall be obtained prior to production. Provide detailed project specifications including single-line diagrams, installation drawings, and applicable standards for engineering review.