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Customer boundary protection
User Boundary Switch
ZW20-12 / ZW139A-12 user boundary vacuum circuit breaker for 10 kV overhead customer demarcation points. It separates user-side ground faults and short-circuit faults from the public feeder so non-fault branches can stay energized.
Specification
12 kV Boundary Switch Ratings
The supplied datasheet gives one 12 kV standard series for 10 kV systems. Use the table to confirm current, short-circuit class, CT/ZCT/PT requirements and environmental conditions before selecting communication or installation details.
12 kV standard series data.
The product is specified as a user boundary vacuum circuit breaker for the demarcation point between grid operator and end user. It integrates the breaker body, CT/ZCT signals, PT supply and FDR boundary controller.
Parameter
Standard data
Rated voltage
12 kV for 10 kV system
Rated frequency
50 Hz
Rated normal current
400 / 630 A
Rated short-circuit breaking current
12.5 / 16 / 20 kA
Rated short-time withstand current
4 s, matched to breaking-current class
Zero-sequence CT range
0-5 A residual current detection
Power-frequency withstand voltage
42 kV for 1 minute
Lightning impulse withstand voltage
75 kV
Mechanical operation life
>=10000 operations
Electrical breaking life
>=30 operations at rated short-circuit class
Secondary circuit withstand
2 kV for 1 minute
Confirm neutral grounding mode before protection settingConfirm PT power supply and communication channel before production
Structure
Breaker Body and Sensing Package
The datasheet treats the product as an integrated boundary protection set: vacuum circuit breaker main body, built-in phase CT, built-in zero-sequence residual CT, external PT and FDR intelligent boundary controller.
Vacuum interrupterSpring mechanismPhase CTZero-sequence CTExternal PTFDR controller
Boundary breaker body
Outdoor vacuum interrupter, spring operating mechanism, epoxy solid insulation bushing and optional isolation disconnector form the main switching body.
Fault signal acquisition
Built-in phase CT and zero-sequence residual CT provide current and residual-current signals for user-side fault judgment.
PT supply and voltage sampling
The external pole-mounted PT supplies controller power and voltage sampling, so the field layout must leave room for the PT and wiring arrangement.
FDR boundary controller
The controller handles protection logic, fault memory, local display, communication module and sealed aviation-plug wiring to the switch body.
Controls
FDR Boundary Controller
The controller compares CT, zero-sequence CT and PT signals with preset thresholds. It trips for user-side ground faults, locks after user-side interphase short-circuit events, records fault data and sends status to a distribution automation system when communication is included.
Single-phase ground fault trip
Detects residual current from the zero-sequence CT and trips the boundary breaker to prevent a user-side ground fault from spreading on the main feeder.
Interphase short-circuit isolation
After the substation outlet breaker trips and recloses, the boundary switch remains open to isolate the faulty customer branch.
Measurement and alarms
Line voltage, phase current and zero-sequence current support overload alarms, overvoltage or undervoltage detection and post-fault maintenance checks.
Communication to DA system
The datasheet lists RS485, DTU wireless communication and compatibility with distribution automation master stations.
Switch body and isolator view
Use this product view when checking the breaker body, isolation handle, phase indicators and pole-mounted operating layout.
PT and controller relationship
Use this view when confirming PT supply, controller interface and wiring relationship before final drawings are approved.
Applications
Customer Boundary Position
Install the switch at the customer demarcation point. The utility feeder remains upstream, while the boundary breaker and FDR controller isolate user-side ground faults or short-circuit faults before they interrupt other branches.
Principle topology at the customer boundaryPower path + fault isolation + DA signal
Electrical path: utility feeder to boundary switch, then to the customer-side branch or incoming line.
Protection path: CT, ZCT and PT signals feed the FDR controller for ground-fault and short-circuit judgment.
Communication path: fault event, switch status and measurement data can be sent to the DA master station.
Endpoint
Path type
RFQ implication
Utility feeder to user incoming line
Power path
Confirm voltage, rated current, short-circuit class and pole installation layout.
CT / ZCT / PT to FDR controller
Protection path
Confirm neutral grounding mode, zero-sequence pickup and PT supply requirement.
Controller to DA master station
Communication path
Confirm RS485, DTU wireless or local-only operation before cabinet configuration.
10 kV T-joint user access
Best fit: overhead T-joint customer access points where user-side faults must be separated from the public feeder.
- Demarcation point
- User-side branch
- Fault isolation
Industrial and mining incoming line
Fit for medium-voltage incoming lines where plant-side faults should not trip upstream network branches.
- Factory incoming line
- FDR controller
- PT power supply
Rural or temporary project supply
Also fits rural-grid and temporary construction supply boundaries where the utility needs clearer responsibility and faster fault location.
- Rural grid
- Project supply
- DA communication option
Factory documents
Boundary Switch Datasheet
The page is based on the English datasheet titled User Boundary Switch (Boundary Circuit Breaker) Full English Datasheet & Specification. It defines aliases, model references, application scope, parameter table, protection principle, structure composition and quotation terminology.
Reference documentUser Boundary Switch full English datasheet.
The datasheet supplies ZW20-12 / ZW139A-12 model references, 12 kV parameters, FDR controller logic and application scope. The matching document can be requested during quotation review.
Technical reviewXIYA POWER sales engineering, June 24, 2026.
The review separates breaker rating, boundary-protection logic, controller communication and RFQ inputs for buyer screening.
Project documentsDatasheet, controller notes and test documents by request.
Ask sales engineering for the English datasheet, controller setting notes, test report or installation drawing that matches the selected project.
ZW20-12 / ZW139A-12
The datasheet names these as representative outdoor vacuum boundary circuit breaker models.
User-side fault isolation
The controller trips or latches the boundary switch for user-side ground faults and interphase short-circuit faults.
PT supply for controller
The external PT provides working power and voltage sampling, reducing the need for separate auxiliary field power.
Outdoor service condition
Datasheet values include -40 deg C to +40 deg C, altitude <=2000 m, pollution class V, wind speed <=35 m/s and ice coating <=10 mm.
RS485 or DTU wireless
Confirm local-only control, RS485, wireless DTU or DA master-station communication before final controller configuration.
Neutral grounding mode matters
The datasheet lists ungrounded, arc-suppression-coil grounded and low-resistance grounded 10 kV grids as applicable modes.
FAQ
User Boundary Switch FAQ
What is a user boundary switch?
A user boundary switch is a medium-voltage vacuum circuit breaker installed at the responsibility demarcation point between the utility feeder and the end user. It isolates user-side faults so the public feeder does not trip for every customer-side failure.
Where is this switch normally installed?
Typical sites include 10 kV overhead distribution T-joint customer taps, industrial incoming lines, rural demarcation points, temporary construction feeds and branch sectionalizing positions.
How is it different from an automatic vacuum circuit recloser?
A user boundary switch focuses on customer-side fault isolation and responsibility demarcation. For broader feeder protection and reclosing, compare the Automatic Vacuum Circuit Recloser.
Does it need an external auxiliary power supply?
The datasheet describes PT voltage supply for the controller, so a separate external auxiliary power source is not the default assumption. Final PT and controller wiring still need project confirmation.
What should be sent for quotation?
Send system voltage, rated current, short-circuit class, neutral grounding mode, boundary point role, installation photo or drawing, PT and controller requirement, communication method, quantity and destination standard.
Boundary Switch RFQ Data
USD 1,800-12,000 reference range depends on rated current, short-circuit class, FDR controller requirement, PT arrangement, communication method, quantity and destination standard. Confirm this is the right product type before sending an RFQ request, then send RFQ details including voltage class, neutral grounding mode, user-side fault scenario, pole installation photo, RS485 or DTU communication need and required documents. To compare adjacent Smart Grid devices, return to the Smart Grid equipment hub, review the Automatic Vacuum Circuit Recloser, compare Cutout Single-Phase Recloser or check the Smart Drop-Out Fuse for fuse-based protection points. For company background, see About XIYA POWER.