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Model-first: JDZW-10R 11kV Cast-Resin Voltage Transformer for Substation Metering and Protection – IEC 61869-3 Certified
Introduction to the JDZW-10R Voltage Transformer
The JDZW-10R is a single-phase, indoor/outdoor-rated cast-resin insulated voltage transformer (VT) designed for accurate voltage measurement and reliable protective relay operation in medium-voltage power systems operating at 11kV (IEC standard) or 10kV (domestic Chinese system). This device leverages advanced vacuum pressure impregnation (VPI) epoxy resin technology to encapsulate its magnetic core and windings, providing superior dielectric strength, mechanical robustness, and environmental resistance compared to traditional oil-immersed designs.
Cast-resin insulation eliminates fire hazards, reduces maintenance requirements, and enables compact physical dimensions—critical advantages in space-constrained substations and urban distribution networks. The JDZW-10R is engineered for long-term stability under continuous electrical stress, thermal cycling, and pollution exposure, making it suitable for both utility-scale infrastructure and industrial facilities.
Operating Principle and Core Construction
The JDZW-10R operates on the fundamental principle of electromagnetic induction. A high-voltage primary winding (rated at 11/√3 kV for phase-to-ground connection in three-phase systems) induces a proportional voltage in one or more secondary windings via a laminated grain-oriented electrical steel (GOES) core. The GOES material minimizes hysteresis and eddy current losses, ensuring high efficiency and low temperature rise during continuous operation. The core is precisely annealed and stacked to reduce magnetostriction, thereby minimizing audible noise and harmonic distortion. The entire magnetic assembly is fully encapsulated in flame-retardant, halogen-free epoxy resin under vacuum conditions, which eliminates air voids and prevents partial discharge inception even at elevated altitudes up to 1000 meters above sea level.
Advantages Over Oil-Immersed Voltage Transformers
Compared to oil-filled VTs, the JDZW-10R offers significant operational and safety benefits. The absence of insulating oil eliminates risks of leakage, fire, and environmental contamination—particularly critical in indoor switchgear rooms, underground substations, and environmentally sensitive zones. Cast-resin construction provides higher short-circuit withstand capability due to rigid mechanical support of windings, reducing deformation under fault currents. Additionally, the solid insulation system exhibits negligible aging under normal service conditions, contributing to a design life exceeding 25 years. Maintenance is simplified to visual inspection only, as there is no need for oil sampling, drying, or topping-up. The unit’s lightweight design (typically 45–55 kg) also facilitates easier handling and installation without specialized lifting equipment.
Typical Deployment Scenarios
The JDZW-10R is commonly deployed in 11kV/10kV distribution substations for dual-purpose applications: revenue metering and protective relaying. In ring main units (RMUs), it supplies scaled-down voltages (e.g., 100/√3 V or 110/√3 V) to energy meters compliant with Class 0.2 or 0.5 accuracy per IEC 61869-3. Simultaneously, its protection-class secondary winding (typically rated 3P or 6P) feeds overvoltage, undervoltage, and directional earth-fault relays. It is also integrated into prefabricated secondary substations, solar PV collector substations, and industrial motor control centers where reliability and minimal footprint are paramount. Its IP2X-rated terminal box ensures safe access during live testing while preventing accidental contact with energized parts.
Technical Specifications
The JDZW-10R adheres strictly to the performance envelopes defined in IEC 61869-3 and GB/T 20840.3, ensuring interoperability across global and domestic grids. Below is a comprehensive specification table followed by environmental and operational parameters.
| Parameter | Value |
|---|---|
| System Voltage (IEC) | 11 kV |
| System Voltage (Domestic) | 10 kV |
| Primary Voltage | 11/√3 kV (phase-to-ground) |
| Secondary Voltages | 100/√3 V (metering), 100/√3 V (protection) – dual secondary optional |
| Voltage Ratio | 11000/√3 : 100/√3 = 110:1 |
| Metering Accuracy Class | 0.2 or 0.5 (per IEC 61869-3) |
| Protection Accuracy Class | 3P or 6P |
| Rated Output (per winding) | 30 VA (metering), 50 VA (protection) – max total 100 VA |
| Insulation Level (LI/AC) | 75 kV / 28 kV (1.2/50 μs lightning impulse and 1-min power frequency) |
| Short-Time Thermal Withstand | 1 second at 100× rated primary current (for fault conditions) |
| Partial Discharge | <10 pC at 1.2 × Um/√3 (Um = 12 kV) |
| Ambient Temperature Range | −25°C to +40°C (standard); −40°C to +45°C (optional cold-climate version) |
| Relative Humidity | Up to 95% non-condensing |
| Altitude | ≤1000 m (derating required above 1000 m) |
| Weight | Approx. 50 kg |
| Dimensions (H×W×D) | 680 mm × 280 mm × 220 mm |
Accuracy and Burden Characteristics
The JDZW-10R maintains its declared accuracy class only when connected to a burden within its rated output range. For Class 0.2 metering, the composite error must not exceed ±0.2% at 80–120% of rated voltage and 25–100% of rated burden. The protection winding (Class 3P) limits voltage error to ±3% and phase displacement to ±60 minutes under similar conditions. Exceeding the rated burden (e.g., connecting multiple meters or long cable runs without compensation) degrades accuracy and may cause saturation during system transients. Recommended maximum secondary cable length is 100 meters for 2.5 mm² copper conductors to keep burden within 30 VA.
Environmental and Service Conditions
Designed for both indoor and outdoor use, the JDZW-10R features UV-stabilized resin housing and corrosion-resistant stainless-steel hardware. The terminal box includes gasket-sealed covers meeting IP2X ingress protection, allowing safe finger access during maintenance. In coastal or industrial atmospheres with high salt or chemical pollution, an optional hydrophobic silicone coating can be applied to the outer surface to prevent tracking. At altitudes above 1000 m, the power frequency withstand voltage must be reduced by 1% per 100 m increment; for example, at 2000 m, the AC test voltage becomes 25.2 kV instead of 28 kV. Continuous operation above 40°C ambient requires derating of output by 1.5% per °C.
Typical Applications
The JDZW-10R serves as a critical interface between high-voltage primary circuits and low-voltage secondary instrumentation across diverse power infrastructure.
Substation Secondary Metering Systems
In 11kV distribution substations, the JDZW-10R provides scaled voltage signals to revenue-class kWh meters, demand recorders, and power quality analyzers. Its Class 0.2 accuracy ensures billing precision within ±0.2%, satisfying regulatory requirements in most jurisdictions. The VT is typically installed on the incoming feeder or busbar section, with secondary wiring routed through shielded cables to the metering panel. Dual-secondary configurations allow segregation of metering and telemetry circuits, enhancing cybersecurity and preventing interference from SCADA polling signals.
Industrial Power Distribution Networks
Large manufacturing plants often operate internal 10kV/11kV distribution systems fed from utility substations. Here, the JDZW-10R supports motor protection relays (e.g., undervoltage lockout for critical pumps), capacitor bank controllers, and arc-flash mitigation systems. Its robust cast-resin body withstands vibrations from nearby heavy machinery, while the high short-circuit withstand rating ensures survival during downstream faults. In facilities with harmonic-rich loads (e.g., variable-frequency drives), the low-loss GOES core minimizes overheating and maintains ratio accuracy despite waveform distortion up to 5% THD.
Renewable Energy Integration Points
Solar and wind farms connect to the grid via 11kV collection feeders. The JDZW-10R monitors voltage at the point of interconnection (POI) for anti-islanding protection, reactive power control, and grid-code compliance reporting. Its fast response time (<20 ms) enables accurate detection of voltage sags during cloud transients or wind lulls. The VT’s immunity to DC offset—common during inverter faults—ensures stable operation where oil-filled units might saturate. Outdoor-rated versions with extended creepage distance (≥25 mm/kV) are used in desert or tropical climates to prevent flashover during dust storms or monsoons.
Rural and Suburban Distribution Feeders
In remote areas with limited maintenance access, the JDZW-10R’s maintenance-free design reduces lifecycle costs. Mounted on pole-top platforms or pad-mounted switchgear, it supplies voltage data to remote terminal units (RTUs) for distribution automation schemes like FLISR (Fault Location, Isolation, and Service Restoration). Its wide temperature tolerance accommodates extreme diurnal swings, while the self-extinguishing resin meets fire safety codes for wooden utility poles. Utilities often specify this model for smart grid rollouts due to its compatibility with digital IEDs requiring analog voltage inputs.
Backup Protection in Ring Main Units (RMUs)
Within SF6 or solid-insulated RMUs, the JDZW-10R acts as a backup voltage source when the main VT fails or during maintenance. It enables manual reclosing verification and post-fault analysis by providing a stable reference during transient recovery. Compact dimensions allow integration into standardized RMU compartments without redesign. The unit’s polarity marking (reducing polarity per IEC 61869-3) ensures correct phasing when paralleled with other VTs in multi-source networks.
Compliance with International Standards
The JDZW-10R is engineered to satisfy the stringent requirements of both international and Chinese national standards, ensuring global acceptance and local regulatory approval.
IEC 61869-3 Certification Details
IEC 61869-3 specifies performance, testing, and marking requirements for inductive voltage transformers. The JDZW-10R complies with all clauses related to accuracy, insulation coordination, temperature rise, and short-circuit behavior. Key tests include: ratio error and phase displacement verification at 20%, 50%, 80%, 100%, and 120% of rated voltage; power frequency withstand at 28 kV for 1 minute; and lightning impulse at 75 kV (1.2/50 μs wave). The manufacturer provides a type test report issued by an ISO/IEC 17025-accredited laboratory, confirming compliance. Markings on the nameplate include In, U1n, U2n, accuracy class, burden, and standard reference (IEC 61869-3).
Alignment with GB/T 20840.3
GB/T 20840.3 is the Chinese national adoption of IEC 61869-3, with minor editorial differences but identical technical content. The JDZW-10R carries dual certification, allowing deployment in State Grid and China Southern Grid projects. Notably, GB/T 20840.3 permits 10kV as the nominal system voltage (vs. 11kV in IEC), but the insulation levels remain identical (LI 75 kV / AC 28 kV). Chinese utilities often require additional factory tests such as partial discharge mapping and thermal imaging under load, which Duomatech performs as part of its quality assurance protocol.
Key Differences Between IEC and Domestic Requirements
While technically harmonized, practical differences exist in documentation and testing emphasis. IEC markets prioritize CE marking and EU-type examination, whereas Chinese projects require CCC (China Compulsory Certification) and submission to provincial grid technical review boards. IEC applications often specify 110/√3 V secondaries, while Chinese systems use 100/√3 V—though the JDZW-10R can be wound for either. Environmental testing under GB/T includes stricter salt fog duration (1000 hours vs. IEC’s 500 hours), reflecting coastal deployment needs. Both standards mandate reducing polarity, but Chinese nameplates additionally display “*” symbols per GB conventions.
On-Site Testing Procedures
Post-installation commissioning tests verify integrity and performance before energization. All procedures follow IEC 61869-3 Annex B and IEEE C57.13 guidelines.
Insulation Resistance Test
Using a 2500 V DC megohmmeter, measure insulation resistance between primary winding and ground, secondary windings and ground, and primary-to-secondary. Acceptance criteria: ≥1000 MΩ at 20°C. Correct for temperature using RT2 = RT1 × 2(T1−T2)/10. Low readings indicate moisture ingress or resin cracking—requiring drying or replacement. Perform before and after high-potential tests to detect insulation degradation.
Turns Ratio Verification
Apply 100–200 V AC to the primary and measure secondary voltage with a calibrated true-RMS multimeter. Calculate actual ratio: U1/U2. Tolerance must be within ±0.2% for Class 0.2 VTs. Use a dedicated ratio tester (e.g., Omicron CT Analyzer) for automated comparison against nameplate values. Deviations >0.5% suggest winding shorts or incorrect tap selection.
Polarity Confirmation
Connect a 6–12 V battery momentarily between primary terminals (H1 to H2). Observe secondary voltage polarity with a DC voltmeter (X1 to X2). A positive kick confirms reducing polarity (standard per IEC 61869-3). Incorrect polarity causes 180° phase reversal, leading to metering errors and relay misoperation. Document results with oscillograph traces if available.
Power Frequency Withstand Voltage Test
Apply 28 kV RMS at 50 Hz between primary and grounded secondary/core for 1 minute. Use a calibrated test transformer with overcurrent trip set at 10 mA. No flashover or breakdown is permitted. Reduce voltage gradually post-test to avoid resonant overvoltages. This test validates insulation integrity after transport and installation stresses.
Open-Circuit Characteristic Test
With secondaries open, apply 20–120% of rated primary voltage in 20% increments. Record excitation current and secondary voltage. Plot knee-point curve to verify core linearity. Excessive magnetizing current (>5 mA at 100% voltage) indicates core damage or shorted turns. This test is critical for protection-class VTs to ensure no saturation during voltage swells.
Preventive Maintenance Guide
Although cast-resin VTs are largely maintenance-free, periodic checks ensure decades of reliable service.
Annual Visual and Functional Inspection
Inspect for surface cracks, tracking marks, or discoloration on the resin housing. Check terminal tightness (torque: 15 N·m for M8 bolts) and corrosion on grounding lugs. Verify nameplate legibility and secondary shorting links are removed during operation. Perform infrared thermography under load: hotspot differentials >10°C above ambient warrant investigation. Clean surfaces with non-abrasive detergent if contaminated with salt or carbon deposits.
Five-Year Dielectric and Accuracy Recalibration
Every 60 months, repeat insulation resistance and turns ratio tests. If installed in harsh environments (chemical plants, coastal zones), add partial discharge measurement using IEC 60270 methods—acceptance limit remains <10 pC. Send one unit per batch to an accredited lab for full accuracy recalibration against reference standards. Replace if ratio error exceeds 70% of original tolerance band (e.g., >±0.14% for Class 0.2).
Fault Diagnosis and Replacement Criteria
Common failure modes include secondary winding opens (causing infinite burden and relay dropout) or resin delamination (leading to partial discharge). Symptoms: erratic meter readings, protection relay alarms, or audible buzzing. If insulation resistance drops below 100 MΩ or PD exceeds 50 pC, replace immediately. Never attempt field repair—cast-resin units are not serviceable. Maintain spare inventory with matched ratio and accuracy class for rapid swap-out. Log all maintenance actions in asset management systems for lifecycle tracking.
Conclusion
The JDZW-10R 11kV cast-resin voltage transformer represents a mature, field-proven solution for accurate metering and dependable protection in modern medium-voltage networks. By leveraging VPI epoxy encapsulation and GOES core technology, it delivers exceptional dielectric performance, thermal stability, and mechanical resilience—surpassing the limitations of legacy oil-immersed designs. Its strict adherence to IEC 61869-3 and GB/T 20840.3 ensures seamless integration into both international and Chinese power systems, with dual 10kV/11kV voltage ratings accommodating regional grid variations. The unit’s maintenance-free operation, compact form factor, and 25–30 year service life significantly reduce total cost of ownership, particularly in remote or space-constrained installations. Rigorous factory and on-site testing protocols guarantee performance within tight tolerances, while robust construction withstands environmental stressors from arctic cold to tropical humidity. For engineers designing or upgrading 11kV distribution infrastructure, the JDZW-10R provides a technically sound, standards-compliant, and operationally reliable voltage sensing solution that supports the evolving demands of smart grids, renewable integration, and industrial electrification. Its combination of precision, durability, and safety makes it a cornerstone component in critical power measurement and protection architectures worldwide.