JDZ9-35, JDZF9-35 Outdoor epoxy resin cast voltage transformer (35kV PT)

2026-03-02

Product Overview

Functional Definition

The JDZ9-35 and JDZF9-35 Outdoor epoxy resin cast voltage transformer are precision electromagnetic instruments designed for accurate voltage measurement, energy metering, voltage monitoring, and relay protection applications in 35kV medium-voltage AC outdoor power systems. These transformers utilize electromagnetic induction principles to provide galvanically isolated secondary voltage signals proportional to primary voltage.

Key Ratings

Item	Specification (per order / nameplate)
System voltage class	35 kV class (outdoor medium-voltage distribution applications)
Rated frequency	50 Hz (60 Hz available upon request)
Rated primary voltage	35000 V (line-to-ground for single-phase; line-to-line variations available)
Rated secondary voltage	100 V or 220 V (line-to-ground); 100/√3 V (for grounded wye configurations)
Accuracy classes	Metering and/or monitoring/protection cores as specified (e.g., 0.2, 0.5, 6P)
Rated burden	Per core/winding as specified (20-90 VA depending on configuration)
Burden power factor	cosφ = 0.8 (lagging) unless otherwise specified by the project standard
Maximum output capacity	300-800 VA depending on model variant
Insulation level	40.5 / 95 / 200 kV (Um / LIWL / ACWL)
Applicable standards	IEC 61869-3; GB/T 20840.1 / 20840.3; GB 1207-2006
Model variants	JDZ9-35 / JDZF9-35 / JDZX9-35G / JDZXF9-35G

Working Principle

Operating on Faraday’s law of electromagnetic induction, the voltage transformer features a laminated magnetic core with primary winding connected to system voltage and secondary windings wound around the core. The alternating magnetic flux generated by primary voltage induces proportional voltage in the secondary winding, delivering standardized output voltage through connected burden. The transformer operates in low magnetic flux density region to ensure linearity and accuracy across the specified voltage range.

System Application Position

Medium Voltage Distribution: 35kV outdoor substations and distribution networks
Energy Metering: Revenue-grade voltage measurement systems for billing applications
Voltage Monitoring: System voltage supervision and power quality monitoring
Protection Circuits: Overvoltage, undervoltage, and directional protection schemes
SCADA Integration: Supervisory control and data acquisition systems

Structural Overview

Epoxy resin cast construction with fully-enclosed design ensures superior insulation performance, UV resistance, moisture resistance, and mechanical strength. The outdoor post-type mounting configuration provides reliable installation in substation environments while maintaining excellent electrical clearance and creepage distances suitable for II-grade pollution environments.

Model Designation

JDZX9 35G JDZ9 35 Cast Resin Voltage Transformers JDZF9 type

Model Code Explanation

J — Voltage transformer (VT)
D — Single-phase configuration
Z — Cast-resin (epoxy) insulated, fully enclosed structure
F — Dual secondary windings (when present)
X — With tertiary winding for open-delta protection (when present)
9 — Design code (platform/iteration)
35 — Voltage class (kV)
G — Grounding application variant (when present)

Variant Differences

Model	Secondary Windings	Typical Application
JDZ9-35	Single secondary winding	Single-purpose metering or monitoring
JDZF9-35	Dual secondary windings	Separate metering and monitoring/protection cores
JDZX9-35G	Dual windings + tertiary winding	Metering, monitoring, and ground fault/open-delta protection
JDZXF9-35G	Three secondary windings	Metering, monitoring, and dedicated protection core

JDZ9-35 and JDZF9-35 variants are electrically compatible when specified with the same voltage ratio, accuracy classes, and burdens. The F-series provides dual independent secondary windings for simultaneous metering and monitoring applications without burden interaction.

Service Conditions

The JDZ9-35/JDZF9-35 series voltage transformers are designed for outdoor operation under normal service conditions in 35kV medium-voltage power systems.

Installation environment: Outdoor installation (post-mounted in substations)
Altitude: Not exceeding 1000 m above sea level (higher altitude shall be specified for engineering confirmation)
Ambient temperature: −25 °C to +40 °C (daily average ≤ 30 °C)
Relative humidity: Daily average ≤ 95%, monthly average ≤ 90%
Pollution grade: Grade II (suitable for areas without severe industrial contamination)
Environmental conditions: No severe corrosive gases, explosive or flammable media; no abnormal vibration or mechanical shock
UV and weather resistance: Epoxy resin structure provides excellent UV resistance and weathering protection

Engineering Note: The installation location shall comply with applicable electrical safety regulations, pollution level assessment, and provide stable operating conditions throughout the transformer’s service life. For altitude > 1000m or pollution grade > II, insulation coordination shall be reviewed.

Construction

Construction Design

Structure: Outdoor post-type for substation installation
Insulation: Fully enclosed epoxy resin cast insulation with integrated structure
Core: Silicon steel laminated core design optimized for low flux density operation
System: Integrated primary and multi-secondary insulation system
Mounting: Bottom-mounted flange with fixing bolt holes
Protection: Optional lightning arrester (zinc oxide) integration available

The epoxy resin casting provides stable insulation properties and resistance to moisture, UV radiation, contamination, and aging for long-term outdoor service in various climatic conditions.

Windings & Terminal Marking

Primary terminals: A / X (high-voltage terminals)
Secondary terminals (Winding 1): a / x or a1 / x1
Secondary terminals (Winding 2): a2 / x2 (JDZF series)
Tertiary terminals (Open-delta): ad / xd (JDZX series)

Terminal markings follow standard VT polarity conventions per IEC 61869-3 and GB/T 20840.3. Under normal operating conditions, when primary terminal A is instantaneously positive with respect to X, secondary terminal a is instantaneously positive with respect to x. Correct terminal identification shall be observed to ensure metering and protection performance.

Grounding Note: One point of the secondary circuit (typically terminal x or x1) must be reliably grounded per applicable standards to ensure personnel safety and proper operation.

Technical Data

This section provides selection-oriented technical data for the JDZ9-35 and JDZF9-35 series outdoor, cast-resin voltage transformers used in 35 kV class AC systems (50 Hz standard, 60 Hz available). Data shown below is intended for preliminary selection of accuracy class combinations, rated burdens, and maximum output capacity.

Definitions: Accuracy class combination indicates available metering/monitoring/protection cores in one VT (multi-core configuration may apply). Rated output (VA) is specified per secondary winding. Maximum output (VA) represents the thermal capacity limit of each winding. Insulation level is specified as Um / LIWL / ACWL where Um = maximum system voltage, LIWL = lightning impulse withstand level, ACWL = AC withstand level.

Notation: Voltage ratios expressed as primary/secondary. For grounded wye systems, line-to-ground voltages apply; divide by √3 where indicated. Acceptance shall be based on nameplate values and factory test report.

Data Reference

Model	Rated Voltage Ratio (V)	Accuracy Class Combination	Rated Output (VA)	Maximum Output (VA)	Insulation Level (kV) Um / LIWL / ACWL
JDZ9-35	35000 / 100 35000 / 220	0.2	50	800	40.5 / 95 / 200
JDZ9-35	35000 / 100 35000 / 220	0.5	90	800	40.5 / 95 / 200
JDZF9-35	35000 / 100 / 100 35000 / 100 / 220	0.2 / 0.2	30/30, 30/50, 50/50	2 × 400	40.5 / 95 / 200
JDZF9-35	35000 / 100 / 100 35000 / 100 / 220	0.2 / 0.5	30/30, 30/50, 50/50	2 × 400	40.5 / 95 / 200
JDZF9-35	35000 / 100 / 100 35000 / 100 / 220	0.5 / 0.5	30/30, 30/50, 50/50	2 × 400	40.5 / 95 / 200
JDZX9-35G	35kV/√3 / 100/√3 / 100/3	0.2 / 6P	30 / 100	600	40.5 / 95 / 200
JDZX9-35G	35kV/√3 / 100/√3 / 100/3	0.5 / 6P	90 / 100	600	40.5 / 95 / 200
JDZXF9-35G	35kV/√3 / 100/√3 / 100/√3 / 100/3	0.2 / 0.2 / 6P	20/20/100	2 × 300 + 100	40.5 / 95 / 200
JDZXF9-35G	35kV/√3 / 100/√3 / 100/√3 / 100/3	0.2 / 0.5 / 6P	25/25/100	2 × 300 + 100	40.5 / 95 / 200
JDZXF9-35G	35kV/√3 / 100/√3 / 100/√3 / 100/3	0.5 / 0.5 / 6P	30/30/100	2 × 300 + 100	40.5 / 95 / 200

Selection Note: When dual or triple windings are specified, each winding’s burden must be calculated independently. Total thermal capacity is distributed among windings; simultaneous operation at maximum burden on all cores may not be permissible without thermal verification.

Application Engineering Support: Application-specific recommendations may include burden calculation, accuracy assessment under various load conditions, thermal rating verification, terminal allocation, and substation integration guidance based on project specification.

Standards & Normative References

Standard	Title	Application
IEC 61869-3	Instrument Transformers – Part 3: Additional Requirements for Voltage Transformers	VT-specific requirements
IEC 61869-1	Instrument Transformers – Part 1: General Requirements	General requirements
GB/T 20840.3	Instrument Transformers – Part 3: Voltage Transformers	National VT standard (aligned with IEC 61869-3)
GB/T 20840.1	Instrument Transformers – Part 1: General Requirements	National general requirements (aligned with IEC 61869-1)
GB 1207-2006	Voltage Transformers	National VT standard where specified by the project
GB/T 22071.1	Insulation Coordination for Medium-Voltage Equipment	Insulation level verification
IEC 60071-1	Insulation Co-ordination – Part 1: Definitions, Principles and Rules	Insulation coordination reference
GB/T 16927.1	High-voltage Test Techniques – Part 1: General Definitions and Test Requirements	Dielectric testing requirements
IEC 60060-1	High-voltage Test Techniques – Part 1: General Definitions and Test Requirements	International dielectric test reference

Factory Test Compliance

Routine tests per applicable IEC/GB requirements (including polarity/marking verification, ratio verification, voltage error and phase displacement verification per specified accuracy class and burden)
Dielectric tests per insulation coordination requirements:
- Power frequency withstand test (ACWL): 200 kV for 1 minute
- Lightning impulse withstand test (LIWL): 95 kV (positive and negative)
Partial discharge test per GB/T 20840.1-2010 and GB/T 20840.3-2013 requirements (≤10 pC at 1.2 Um)
Temperature rise test under rated burden to verify thermal performance
Visual and dimensional inspection including marking, workmanship conformity, and installation interface verification
Type and special tests as required by the project specification

Compliance Note: All variants maintain full compliance with listed standards. Type test certificates and routine test reports are available for each manufactured unit with traceability to accredited laboratories per CNAS/ILAC requirements.

Installation & Dimensions

Outline dimensions and mounting details are provided in the dimensional drawings.
The transformer shall be securely mounted using the bottom flange fixing holes with appropriate hardware.
Primary connection is made via high-voltage busbar or terminal connector at terminal A.
Terminal X must be properly grounded per system grounding practice.
Adequate clearance shall be maintained for insulation coordination, heat dissipation, and maintenance access.
Lightning protection (surge arrester) shall be installed per project requirements.

Clearance Requirements: Minimum phase-to-phase and phase-to-ground clearances shall comply with GB 50060 and local utility standards for 35kV outdoor installation. Typical minimum clearances: phase-to-ground ≥ 300mm, phase-to-phase ≥ 500mm under normal conditions.

Outline Drawings

JDZX9 35G JDZ9 35 Cast Resin Voltage Transformers JDZF9 outline

JDZ9-35 / JDZF9-35

Wiring Diagram

JDZX9 35G JDZ9 35 Cast Resin Voltage Transformers JDZF9 principle diaram

Connection Schematic

Safety Notice: Secondary circuits must be grounded at one point per applicable standards. Before any secondary circuit work, the primary circuit must be de-energized and grounded, or appropriate isolation procedures must be followed in accordance with local electrical safety regulations.

Safety Notes

Secondary circuit must have one point reliably grounded (typically terminal x or x1) to ensure personnel safety and proper operation.
During inspection or maintenance, the primary circuit must be de-energized, isolated, and grounded before any work on secondary circuits.
Fuses or circuit breakers shall be installed in secondary circuits for protection against short circuits.
All installation and maintenance work shall comply with local electrical safety regulations and utility standards.
Regular inspection of epoxy resin surface condition, terminal connections, and grounding integrity is recommended.

Ordering Information

When placing an order, the required configuration shall be specified according to the local grid requirements, applicable standards, and project technical specification. The following parameters shall be clearly stated for technical confirmation and production release:

Rated primary voltage (35000 V or 35kV/√3 for grounded systems)
Rated secondary voltage (100 V, 220 V, or 100/√3 V as applicable)
Number of secondary windings (single, dual, or triple winding configuration)
Application and accuracy requirements (metering and/or monitoring/protection accuracy class combination)
Rated burden (VA) for each secondary core/winding
Insulation level requirements (standard or enhanced for high-altitude/pollution)
Frequency (50 Hz standard; 60 Hz if required)
Special features (if any): lightning arrester integration, enhanced UV protection, special mounting arrangements

If local utility or project requirements apply (e.g., enhanced insulation level, specific partial discharge limits, terminal arrangement, auxiliary equipment integration, mounting constraints, documentation language, or required certificates), specify them at the ordering stage. Special configurations shall be confirmed by technical agreement and final datasheet prior to production.

Customization Available: Non-standard voltage ratios, special accuracy combinations, enhanced environmental protection, and integrated auxiliary equipment can be provided upon request with technical confirmation.

FAQs

Q1: What are the typical applications for JDZ9-35 voltage transformers?

JDZ9-35 series are used in 35kV outdoor substations and distribution networks for energy metering, voltage monitoring, power quality assessment, and relay protection. Typical installations include utility substations, industrial power distribution systems, wind farms, and solar power plants.

Q2: How does epoxy resin insulation benefit outdoor voltage transformer performance?

Epoxy resin casting provides excellent UV resistance, moisture immunity, resistance to contamination and aging, and superior mechanical strength. These properties significantly extend service life, reduce maintenance requirements, and ensure reliable operation in diverse outdoor environmental conditions compared to traditional oil-paper insulation.

Q3: What is the difference between JDZ9-35 and JDZF9-35 models?

JDZ9-35 features a single secondary winding for single-purpose applications. JDZF9-35 incorporates dual independent secondary windings, allowing simultaneous metering and monitoring/protection functions without burden interaction. The F-series provides greater flexibility for modern substation configurations requiring separate circuits.

Q4: How to determine the appropriate rated burden (VA) for secondary circuits?

Calculate total connected burden by summing all instrument burdens (meters, relays, indicators) plus wiring losses (I²R). For 100V secondary at 0.5A nominal current, typical burdens range from 20-90 VA. Ensure selected VT rated burden exceeds calculated burden with appropriate margin (typically 20-30%) for accuracy and thermal performance.

Q5: Are non-standard voltage ratios available for special applications?

Yes. While standard ratios are 35000/100V and 35000/220V, custom voltage ratios can be manufactured upon request with technical confirmation. Applications may include special metering systems, legacy equipment interfacing, or non-standard system configurations.

Q6: What are the grounding requirements for JDZ9-35 secondary circuits?

One point of each secondary circuit (typically terminal x or x1) must be solidly grounded per IEC 61869-3 and GB/T 20840.3 requirements. This ensures personnel safety, prevents dangerous voltages on secondary terminals during insulation failure, and provides reference potential for protective relaying.

Q7: How is compliance with partial discharge requirements verified?

All units undergo partial discharge testing per GB/T 20840.1-2010 and GB/T 20840.3-2013. Maximum permissible partial discharge is ≤10 pC at 1.2 × Um (maximum system voltage). Test certificates with traceable measurement data are provided with each unit documenting compliance.

Q8: Can JDZ9-35 transformers be used at altitudes above 1000m?

Yes, but insulation coordination must be reviewed. At higher altitudes, air density decreases, reducing external insulation strength. Altitude correction factors per IEC 60071-1 shall be applied to verify clearances and creepage distances. Enhanced insulation designs are available for high-altitude applications.

Q9: What maintenance is required for outdoor epoxy resin voltage transformers?

Maintenance requirements are minimal due to sealed construction. Recommended practices include: periodic visual inspection of epoxy surface condition, terminal connection tightness verification, grounding integrity checks, and cleaning of contamination deposits in polluted environments. Typical inspection interval: annual or per local utility standards.

Q10: How do JDZX9-35G models provide ground fault protection?

JDZX9-35G incorporates a tertiary winding connected in open-delta (broken-delta) configuration across three units. During ground faults, zero-sequence voltage appears across the open-delta winding, providing signal to ground fault relays. The 100/3 V tertiary winding with 6P accuracy is specifically designed for this protection function.

Thomas Electric

Thomas Electric News

News & Resources

Categories