KYN28 Switchgear – Composition and Manufacturing Process

1. Composition of KYN28 Switchgear

KYN28 (also known as KYN28-12 armored withdrawable metal-clad switchgear) is a 10 kV distribution assembly widely used in power systems. It consists of two main parts—the enclosure and the withdrawable truck (draw-out circuit-breaker compartment). Internally it is divided into four independent, fully segregated functional compartments:

Compartment	Main Components & Function
Instrument Compartment	Houses micro-processor relays, meters, indicators, push-buttons, and other secondary devices for monitoring and protection.
Circuit-Breaker Compartment (Truck Bay)	Contains a withdrawable vacuum circuit-breaker truck (e.g., VS1 or VD4) with three defined positions—service, test, and isolated. Features shutter mechanisms and guide rails.
Busbar Compartment	Houses three-phase main and branch busbars, fully insulated by sleeves or boots, supporting high-current systems and preventing arc propagation.
Cable Compartment	Accommodates current transformers, earthing switches, surge arresters, and cable terminations. Spacious enough for up to six single-core cables in parallel.

Additional elements include pressure-relief channels and a complete “five-prevention” interlock system (against mis-operation, live switching, energised earthing, etc.).

2. Manufacturing Process of KYN28 Switchgear

Manufacturing is characterised by high modularity, standardisation, and intelligent quality control. Key steps are:

2.1 Enclosure Fabrication

• Material: 2 mm thick Aluzinc or hot-dip-galvanised steel sheet for superior oxidation and corrosion resistance.
• Machining: CNC turret punching and multi-bend forming ensure dimensional accuracy and interchangeability.
• Assembly: High-tensile bolted or riv-nut construction eliminates welding distortion and allows rapid field assembly.

2.2 Surface Protection

• Electrostatic powder coating or epoxy-polyester spray to achieve IP4X protection and long-term corrosion resistance.

2.3 Busbar Processing

• Copper bars are tin-plated or sleeved with heat-shrink insulation; aluminium bars are wrapped with insulating sleeves.
• Insulating boots or covers on joints prevent arc tracking.
• For ratings ≥ 2500 A, busbar chambers include additional epoxy insulators to prevent deformation under short-circuit forces.

2.4 Truck & Interlock System

• Truck movement via a precision lead-screw mechanism for smooth, accurate positioning.
• Mechanical and electrical dual interlocks ensure operator safety and prevent mal-operation.

2.5 Intelligence & Testing

• Optional integration of temperature/humidity sensors, partial-discharge monitors, and intelligent operator interfaces for remote diagnostics.
• Routine tests: power-frequency withstand voltage, mechanical endurance (≥10 000 operations), and interlock-function verification before shipment.

Structural Layout (Schematic)

┌──────────────┐
│ Instrument Compartment (Top)   │ ← Secondary control & protection
├──────────────┤
│ Busbar Compartment (Upper Rear)│ ← Main & branch busbars
├──────────────┤
│ Circuit-Breaker Compartment    │ ← Withdrawable vacuum breaker
├──────────────┤
│ Cable Compartment (Lower)      │ ← Cables, CTs, VTs, arresters
└──────────────┘

KYN28 Switchgear
Assembly & Test Process Flow

The following flow is based on a proven production line with an annual output of 5 000 units. “Assembly” and “Testing” are divided into 14 key stations (S0–S13). Each station lists the main tasks, quality-control points (QC), required records, and tooling/fixtures; the data can be dropped directly into work instructions (WI) or standard operating procedures (SOP).

1 Process Overview

Phase	Station	Name	Purpose	Takt	Key Record
Prep	S0	Material kitting & IQC	Prevent wrong/mixed parts	30 min	Incoming-inspection sheet
Build	S1	Frame assembly	Ensure geometric accuracy	20 min	Assembly checklist
Build	S2	Partition/rail mounting	Form separate compartments	15 min	Dimension check sheet
HV	S3	Busbar fabrication & mounting	Current-carrying & dynamic stability	25 min	Busbar log
HV	S4	CT & surge-arrester mounting	Measuring & over-voltage protection	10 min	Torque record
LV	S5	Secondary harness pre-fab	Reduce on-site wiring	30 min	Wire list
LV	S6	Secondary wiring & termination	Signal integrity	25 min	Continuity test log
Mech	S7	Truck / breaker insertion	Mechanical fit	10 min	Truck interchange log
Mech	S8	Mechanical interlock adjustment	“Five-prevention” verification	15 min	Interlock test sheet
Close	S9	Cover & pressure-relief mounting	IP & relief path	10 min	Visual-inspection sheet
Test	S10	Power-frequency withstand test	42 kV / 1 min	8 min	HV test report
Test	S11	Relay setting & functional test	Secondary-system correctness	20 min	Relay sheet
Final	S12	Final factory acceptance test	Full-item FAT	15 min	FAT report
Ship	S13	Packing & dispatch	Anti-corrosion, anti-shock	10 min	Packing list

Total takt ≈ 3.5 h/unit (one 8-hour shift yields 2 units).

2 Detailed Process Steps

S0 Material Kitting & IQC

• Tasks: Scan barcode → verify specs → random visual/dimensional check → affix IQC PASS label.
• QC: Copper bus thickness; tin-plating ≥ 8 µm; insulation parts UL94 V-0.

S1 Frame Assembly

• Tasks:

1. Assemble Aluzinc side frames, cross beams and base plate with M8 bolts + riv-nuts;
2. Use 3-D right-angle fixture: diagonal error ≤ 1 mm.

• Tooling: Pneumatic torque wrench 25 N·m.

S2 Partition / Rail Mounting

• Tasks: Mount metal partitions, shutter mechanisms, truck rails; conductive paste on grounding lugs—surface must be metal-bright.
• QC: Rail horizontality ≤ 0.5 mm / 1 000 mm.

S3 Busbar Fabrication & Mounting

• Tasks:

1. CNC busbar machine performs punching, chamfering and embossing in one pass;
2. Heat-shrink tube oven 120 °C / 10 min;
3. After mounting, re-torque M12 bolts to 50 N·m.

• QC: Contact resistance ≤ 20 µΩ.

S4 CT & Surge-Arrester Mounting

• Tasks: Remove CT secondary shorting links before installation; arrester ground lead directly to main earth bar.
• Record: CT ratio & polarity measured values.

S5 Secondary Harness Pre-Fabrication

• Tasks: Automatic cut-strip-crimp machine cuts wire → crimps terminals → inserts heat-shrink sleeves → 100 % continuity check.
• QC: Wire diameter tolerance ±0.1 mm; crimp height per JST standard.

S6 Secondary Wiring & Termination

• Tasks:

1. Route wires in trunking; bend radius ≥ 6D;
2. Terminal screws torque 0.8 N·m;
3. Check continuity & insulation > 100 MΩ (DC 500 V).

S7 Truck / Breaker Insertion

• Tasks:

1. Apply conductive grease No. 3 on plug-in contacts;
2. Two intermediate stops to verify shutter opening/closing synchronism;
3. Interchangeability check: insertion force ≤ 300 N for same-type trucks.

S8 Mechanical Interlock Adjustment

• Tasks:

1. Manual & electrical open/close 50 cycles, record timing;
2. Verify five-prevention functions:
   • Earth switch ON → truck cannot be racked-in;
   • Breaker closed → door electromagnetic lock cannot be released.

• Tooling: Mechanical-characteristic tester.

S9 Cover & Pressure-Relief Plate Mounting

• Tasks: Fit explosion-proof film inside relief plate; add spring washers to bolts; check IP4X slot gap ≤ 2.5 mm.

S10 Power-Frequency Withstand Test

• Conditions: phase-to-phase & phase-to-earth 42 kV / 1 min; across open contacts 48 kV / 1 min; leakage ≤ 10 mA.
• Safety: 8 mm insulating mat, audible-visual alarm, access interlock.

S11 Relay Setting & Functional Test

• Tasks:

1. Inject secondary current with relay test set to verify over-current, instantaneous, earth-fault;
2. Simulate undervoltage & anti-pumping circuits;
3. Record pick-up, reset ratio, operating time.

S12 Final Factory Acceptance Test (FAT)

• Per GB 3906-2020:
• Visual, mechanical operation, interlocks, insulation, main-circuit resistance, secondary-circuit withstand, instrument indication consistency.
• Issue stamped FAT report.

S13 Packing & Dispatch

• Tasks:

1. Vacuum bag + desiccant + anti-shock foam;
2. Wooden crate labels “UP”, “MOISTURE PROOF”, “DO NOT INVERT”;
3. ERP scan-out, transport tracking number sent to customer.

3 Quality-Control Summary

Item	Standard	Instrument	Frequency
Frame diagonal difference	≤ 1 mm	Steel tape	100 %
Busbar joint resistance	≤ 20 µΩ	Loop-resistance tester	Each unit
Secondary insulation	≥ 100 MΩ	500 V megger	100 %
Power-frequency withstand	42 kV / 1 min no flashover	HV test set	100 %
Mechanical life	10 000 ops no fault	Mechanical tester	Type test

4 Man-Hours & Manpower (per unit)

• Structure assembly: 2 workers × 60 min
• HV installation: 2 workers × 35 min
• Secondary wiring: 2 workers × 55 min
• Test & commissioning: 2 workers × 43 min
• Packing: 1 worker × 10 min

Total: 9 man-hours/unit (excluding material handling).