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JDZ(X)W-33 Outdoor Voltage Transformer - 33kV, Epoxy-Cast
- Overview
- Applications
- Technical Data
- Services
- Quality Control
- Recommended Products
JDZ(X)W-33 Outdoor Voltage Transformer - 33kV, Epoxy-Cast
JDZ(X)W-33 series are outdoor single-phase epoxy-resin cast voltage transformers for 33kV medium-voltage distribution systems at 50Hz or 60Hz. Built to IEC 61869-3 and GB/T 20840.3, they provide accurate voltage measurement, revenue metering and protection relay supply for 33kV switchgear, substations and ring main units across Africa, South Asia and Southeast Asia.
The series covers four variants matched to different secondary winding configurations:
- JDZW-33: single primary, single secondary, ratio 33/0.11 kV. Standard metering and protection unit for grounded-neutral 33kV systems.
- JDZ9-33: as above with ratio 33/0.1 kV, an alternative secondary voltage for specific relay and meter schedules.
- JDZXW-3: single primary, triple secondary (1a1n metering / 2a2n indication / dadn residual), ratio 33/√3 to 0.11/√3 kV. For earthed-neutral networks where a residual voltage winding is required for earth-fault protection.
- JDZX9-3: as JDZXW-3 with the same three-winding configuration and insulation level, alternative dimensional variant.
WHAT A VOLTAGE TRANSFORMER DOES AND WHY THE SPECIFICATION MATTERS
A voltage transformer scales high primary voltage down to a standard 100V or 110V secondary that meters, protection relays and SCADA systems can use safely. Accuracy class governs measurement quality: class 0.2 is specified for revenue metering and energy management where billing accuracy is the commercial obligation; class 0.5 is sufficient for panel indication, power factor measurement and non-billing instrumentation; protection class 6P or 3P is specified for relay circuits where the VT must remain accurate during a fault.
Burden must be checked against the secondary circuit. A VT delivers rated accuracy only up to its rated output VA. Over-burdened VTs are out of class regardless of nameplate rating, and in a revenue metering application that means the meter is legally incorrect.
EPOXY-CAST CONSTRUCTION FOR OUTDOOR SERVICE
The active parts are fully encapsulated in flame-retardant cycloaliphatic epoxy resin, sealed against moisture, dust, salt fog and UV degradation. No oil, no breathing, no periodic oil sampling. This is what makes epoxy-cast construction the standard choice for outdoor 33kV installations across coastal Africa, the Gulf and South Asia, where conventional oil-filled units require regular oil maintenance and oil disposal in markets where those services are not readily available.
VOLTAGE FACTOR AND NEUTRAL EARTHING
For JDZXW-3 and JDZX9-3 three-winding variants, the rated voltage factor must be specified to match the network earthing arrangement. On a solidly earthed 33kV system, 1.2 continuous is standard. On an isolated or resonant-earthed neutral, specify 1.9 for 30 seconds, which allows the relay to see the full displacement voltage during a single-phase earth fault without the VT core saturating.
PRIMARY APPLICATIONS
- Revenue and sub-billing energy metering at 33kV - specify class 0.2 on the metering winding (1a1n) to meet utility billing accuracy requirements. A class 0.5 VT where 0.2 is required means the meter is contractually incorrect.
- Busbar voltage measurement and indication in 33kV switchgear panels - class 0.5 on the indication winding (2a2n) for panel voltmeters, synchroscopes and SCADA voltage inputs.
- Earth-fault and residual overvoltage protection using the open-delta (dadn) winding of JDZXW-3 and JDZX9-3 variants - the residual winding delivers the displacement voltage signal to the earth-fault relay during a single-phase fault on isolated or resistance-earthed networks.
- Transformer primary protection on 33kV feeder circuits, providing the voltage reference for directional overcurrent and distance protection relays.
- Synchronising and auto-reclose voltage check on 33kV bus-coupler and bus-section panels.
- Capacitor bank protection and measurement on 33kV compensation banks.
- Solar PV and wind farm 33kV step-up substation metering and protection panels, particularly in coastal and desert sites where sealed epoxy construction is essential.
- Utility distribution substations on 33kV networks across Sub-Saharan Africa, South Asia and Southeast Asia.
- Industrial plant primary substations taking a 33kV supply in mining, steel, cement and petrochemical facilities.
- Retrofit into existing 33kV switchgear where the original oil-filled VT is life-expired or leaking.
WINDING SELECTION GUIDE
- JDZW-33 / JDZ9-33: single secondary, for straightforward metering and protection where a separate residual winding is not required. Simpler secondary circuit, lower burden allocation.
- JDZXW-3 / JDZX9-3: triple secondary, for networks requiring simultaneous revenue metering (0.2 class), indication (0.5 class) and earth-fault protection (6P class) from a single primary unit. The dadn open-delta winding is mandatory for earth-fault relay supply on isolated and resistance-earthed 33kV networks.
REGIONAL FIT
- Africa: 33kV networks across Nigeria, Kenya, South Africa, Ghana, Tanzania and Uganda. Outdoor epoxy-cast construction suited to tropical humidity, coastal salt fog and industrial pollution environments.
- South Asia: 33kV distribution in India, Pakistan, Bangladesh and Sri Lanka. Available at 50Hz.
- Southeast Asia: 33kV industrial and utility substations at 50Hz.
- Middle East: 33kV industrial plant supplies. Saudi Arabian projects verified at 60Hz on request.
NOT SUITABLE FOR
Indoor installation in enclosed switchgear without a weatherproof enclosure - specify an indoor VT variant. Systems below 33kV - specify JDZXW-11 or equivalent 12kV class. Systems above 33kV - specify the 66kV or 110kV class. Revenue metering applications using the indication winding (0.5 class) without a separate 0.2 class metering winding - the accuracy class must match the billing obligation.
TECHNICAL DATA - JDZ(X)W-33 Voltage Transformer Series
Compliance: IEC 61869-3, GB/T 20840.3
| Item | JDZW‑33 | JDZ9‑33 | JDZXW‑3 (three‑winding) | JDZX9‑3 (three‑winding) |
| Rated voltage ratio | 33 / 0.11 kV | 33 / 0.1 kV | 33/√3 kV (primary) | 33/√3 kV (primary) |
| Secondary rated voltages | ‑ | ‑ | 1a1n: 0.11/√3 kV 2a2n: 0.11/√3 kV dadn: 0.11/√3 kV | 1a1n: 0.11/√3 kV 2a2n: 0.11/√3 kV dadn: 0.11/√3 kV |
| Rated frequency | 50 Hz / 60 Hz | 50 Hz / 60 Hz | 50 Hz / 60 Hz | 50 Hz / 60 Hz |
| Rated output‑0.2 class winding | 60 VA | 60 VA | 1a1n: 30 VA | 1a1n: 30 VA |
| Rated output‑0.5 class winding | 120 VA | 120 VA | 2a2n: 50 VA | 2a2n: 50 VA |
| Rated residual winding output | ‑ | ‑ | dadn: 100 VA | dadn: 100 VA |
| Maximum output | 600 VA | 600 VA | 500 VA | 500 VA |
| Measuring winding accuracy | ‑ | ‑ | 1a1n: 0.2 2a2n: 0.5 dadn: 6P | 1a1n: 0.2 2a2n: 0.5 dadn: 6P |
| Rated insulation level | 40.5 kV / 95 kV (BIL) / 185 kV (SI) | 40.5 kV / 95 kV (BIL) / 185 kV (SI) | 40.5 kV / 95 kV (BIL) / 185 kV (SI) | 40.5 kV / 95 kV (BIL) / 185 kV (SI) |
| Net / gross weight | 105 kg / 112 kg | 95 kg / 102 kg | 58.5 kg / 65 kg | 55.5 kg / 62 kg |
| General insulation | Outdoor cycloaliphatic epoxy resin, fully encapsulated | |||
| Mounting | Outdoor, vertical or angled bracket | |||
| Service conditions | Suitable for outdoor installation, coastal and industrial pollution environments | |||
| Note | Accuracy levels and secondary winding parameters can be customised on request |
PRE-SALES SELECTION
- Winding configuration review against the protection and metering schedule: single-secondary JDZW-33 / JDZ9-33 for straightforward metering and protection; three-winding JDZXW-3 / JDZX9-3 where simultaneous revenue metering, indication and earth-fault relay supply are required from a single primary unit.
- Voltage factor specification against the network earthing arrangement. Solidly earthed 33kV networks: 1.2 continuous. Isolated or resistance-earthed neutral: specify 1.9 for 30 seconds so the residual winding can supply the earth-fault relay across the full fault duration without VT core saturation.
- Secondary burden calculation. Provide the relay and meter VA schedule plus secondary cable lengths and we will confirm the winding can carry the connected burden within its rated VA at the required accuracy class.
- Secondary voltage ratio selection: 33/0.11 kV (JDZW-33) or 33/0.1 kV (JDZ9-33) matched to the relay and meter input voltage specification. Confirm before ordering - ratio errors require a transformer replacement, not a relay setting adjustment.
- Non-standard accuracy class combinations and output VA ratings available on request.
MARKET ACCESS AND DOCUMENTATION
- Type-test reports to IEC 61869-3 / GB/T 20840.3 issued with the shipment.
- Third-party certification (KEMA, ASTA, CESI, TUV) available where tender documents require witnessed evidence.
- Certification support for SASO SABER, SONCAP, KEBS PVoC, ICIGI and GOST R submissions where required for the destination market.
TESTING AND DELIVERY
- 100% routine testing before dispatch per IEC 61869-3: ratio and polarity verification, insulation resistance, power-frequency withstand, burden and accuracy class confirmation across the full voltage range.
- Individual routine test certificate supplied per serial number.
- Export packing with desiccant and moisture barrier for seaborne shipment.
- Documentation: routine test report, type-test certificate, dimensional drawing, wiring schematic, spare parts list.
AFTER-SALES
- Installation and commissioning guidance, including secondary circuit burden verification and polarity confirmation.
- Replacement units confirmed against original mounting and terminal dimensions before dispatch - direct retrofit without switchgear modification.
- Technical response within 24 hours.
- Warranty: 18 months from delivery or 12 months from commissioning, whichever expires first.
TYPE TESTING
- Type tested to IEC 61869-3 / GB/T 20840.3: ratio accuracy across the full burden range, insulation withstand (power-frequency, lightning impulse and switching impulse), temperature rise, short-time thermal current withstand, and mechanical endurance.
- Third-party type-test reports from KEMA, ASTA, CESI or TUV available where utility and EPC procurement requires witnessed evidence rather than a manufacturer's own record.
INCOMING MATERIAL CONTROL
- Cycloaliphatic epoxy resin accepted against batch certificate of conformity; material qualification controls the dielectric and UV-resistance properties of the finished encapsulation.
- Magnetic core material verified for grade and cross-section; core grade determines the accuracy class linearity and the protection winding saturation characteristic.
- Primary and secondary winding wire diameter and insulation class verified per batch.
- Nameplate accuracy checked for ratio, accuracy class, burden, insulation level and rated voltage factor before assembly.
IN-PROCESS INSPECTION
- Epoxy casting process monitored and recorded: temperature profile, vacuum level and cure cycle. Voids in the encapsulation are the primary outdoor insulation failure mode and vacuum casting is the control measure.
- Dimensional check after moulding: insulating body height, creepage path length and mounting interface verified against drawing.
- Turns ratio verified on primary and all secondary windings before encapsulation.
- Partial discharge test on encapsulated body: discharge above threshold indicates a void and the unit is rejected.
ROUTINE TESTING - 100%, NO SAMPLING
- Ratio and polarity verification at rated burden on all secondary windings.
- Accuracy class confirmation at 80%, 100% and 120% of rated voltage for metering windings; at rated voltage for protection windings.
- Power-frequency withstand voltage on primary winding to earth and across secondary terminals.
- Insulation resistance on all windings.
- Composite error verification on protection class windings.
- Serialised routine test report issued with every unit.
TRACEABILITY AND SYSTEM
- ISO 9001 quality management system.
- Serial number traceability to epoxy batch, core material batch and winding production record.
- Permanent nameplate with ratio, accuracy class, burden, insulation level, rated voltage factor, serial number and manufacturing date.
- Test records retained for the warranty period and available on request.
