66KV to 132KV Cables Tests requirement

Here’s a detailed breakdown of the required tests for 66 kV and 132 kV XLPE cables per IS 7098 (Part 3) (covering 66 kV up to and including 220 kV), with reference to IS 60840 equivalents where applicable:

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IS 7098 (Part 3): Tests for 66 kV & 132 kV XLPE Cables

Based on the BIS Product Manual for IS 7098 (Pt 3), the following tests are specified—applicable to each completed length of cable and per manufacturing batch/consignment (BIS):

📋 Test Checklist for 66 kV & 132 kV XLPE Power Cables

Standards Referenced: IS 7098 (Part 3), IS 60840 / IEC 60840

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1. Routine Tests (Every Delivered Cable Length)

Test	Sequence	Acceptance Criteria
Conductor resistance	Pre-insulation	≤ values specified in IS 7098 (as per cross-section & temp. corrected to 20 °C)
Partial Discharge (PD) test	After manufacturing, before HV	PD ≤ 5 pC at 1.5 × U₀ (U₀ = phase-to-earth voltage)
High Voltage (HV) test, 1 min	After PD test	Withstand: 160 kV (66 kV class), 275 kV (132 kV class), no breakdown
Conductor & sheath inspection	Visual & dimensional	Within tolerance of IS 7098 Pt-3

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2. Sample Tests (One Length per Batch / Consignment)

Test	Sequence	Acceptance Criteria
Check of cable dimensions	Pre-electrical	Within IS 7098 tolerances
Tensile strength & elongation (insulation/sheath)	Before ageing	≥ 12.5 N/mm² tensile; ≥ 200% elongation
Hot set test (XLPE insulation)	200 °C, 20 N/cm²	Elongation ≤ 175%, permanent set ≤ 15%
Shrinkage test (insulation)	Post heating	≤ 4%
Water penetration (if required)	Longitudinal / radial	No water ingress in defined period
Dielectric power factor & capacitance	Ambient & elevated temp.	Tan δ ≤ 0.001 at U₀, stable trend
Bending test + PD	Mechanical + electrical	No cracks; PD ≤ 5 pC
Flammability (PVC sheathed cables)	Vertical flame test	Self-extinguish within 60 s

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3. Type Tests (Once per Design / Before Approval)

Test	Sequence	Acceptance Criteria
Lightning impulse withstand	After routine HV test	Withstand: 350–380 kV (66 kV); 650 kV (132 kV), no flashover/breakdown
Load cycle test (with PD monitoring)	Repeated heating/cooling cycles	PD ≤ 5 pC throughout; no failure
Long-term thermal ageing (insulation/sheath)	Accelerated ageing	Retention ≥ 80% tensile & elongation
Resistance of semi-conducting layers	As per IS 7098	≤ specified Ω·m resistivity
Short-circuit withstand test	Calculated or tested	Cable survives specified kA²s duty without damage
Impulse + Power frequency withstand of accessories (joints/terminations)	After installation simulation	No breakdown; PD ≤ 5 pC

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Notes

·         Sequence: Mechanical/physical tests → PD → 1-min HV → Impulse withstand (for type) → Load cycle.

·         Acceptance: Any failure in routine test → reject length. Any failure in sample/type test → corrective action + retest.

·         Reference Um values:

o    66 kV cables → Um = 72.5 kV

o    132 kV cables → Um = 145 kV

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✅ This checklist is structured for FAT / vendor QA:

·         Routine = each cable length

·         Sample = one per batch/consignment

·         Type = once per design

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Do you want me to also format this into a professional table layout (Word/PDF-style) with company logo placeholders so you can use it directly in vendor FAT documentation?

 Summary Table: IS 7098 (Pt 3) Key Tests for 66 kV & 132 kV XLPE Cables

Test Category	IS 7098 Pt 3 Requirements (Frequency)
Conductor & Material Properties	Annealing, resistance, screening, insulation, armouring (each length or batch)
Sheath & Insulation Physical Tests	Thickness, tensile, hot set, shrinkage, aging (length-wise or batch-wise)
Semi-Conducting Layer Resistivity	Monthly sampling
Electrical & Dielectric Tests	Dielectric power factor, capacitance, load cycle, impulse, PD, HV withstand (daily to fortnightly)
Thermal & Environmental Durability	Thermal ageing, water tightness, bending + PD, flammability (monthly to quarterly)
Optional Tests	Cold impact, spark voltage on outer sheath (as agreed)

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In Summary

·         66 kV and 132 kV XLPE cables under IS 7098 (Part 3) must undergo a comprehensive suite of type, routine, and acceptance tests, covering physical, mechanical, electrical, and environmental performance aspects.

·         Many of these parallel the IEC 60840 standard’s requirements for high-voltage extruded cable systems (30–150 kV), ensuring a globally aligned framework.

·         Frequency varies: some tests are mandatory per length, others per batch/consignment, and system-level electrical tests (e.g., impulse, load cycling, PD) follow a stricter routine (daily, fortnightly, monthly, or quarterly).

Nice — here are the standard numeric test voltages you asked for (power-frequency 1-minute and lightning-impulse) that are normally applied to 66 kV and 132 kV XLPE cable systems. I pulled these from IEC 60840 / allied technical specs and BIS product material so you can use them directly in test procedures or technical specifications.

Quick note: in standards/workspecs the cable rated/system voltages are often expressed as the highest system voltage (Um). In practice 66 kV class equipment is normally treated as Um = 72.5 kV and 132 kV as Um = 145 kV; test voltages in IEC/IS are defined against those class voltages. The tables below therefore use the commonly adopted Um equivalents.

Recommended test voltages (typical values used in IEC 60840 / practice)

Cable class (nominal)	Common Um used in standards	Power-frequency withstand (r.m.s.) — 1 min	Lightning impulse withstand (1.2/50 µs) — peak
66 kV	72.5 kV	~160 kV (rms) — 1 min. (Tianan Group)	~350 – 380 kV (peak) (commonly quoted 350–380 kV for 72.5 kV class). (Tianan Group, Hitachi Energy)
132 kV	145 kV	~275 kV (rms) — 1 min (often specified as 275 kV). (Hitachi Energy, Bharat Heavy Electricals Limited)	~650 kV (peak) (typical lightning impulse level for 145 kV class). (Hitachi Energy, Bharat Heavy Electricals Limited)

Additional clarifications & practical points

·         Duration & waveforms: the power-frequency test is normally applied for 1 minute (r.m.s. sinusoidal). The lightning test is standard 1.2/50 µs impulse (peak) as per IEC conventions.

·         Where these appear in standards: IEC-60840 contains the normative relationships/tables that give test voltages related to rated voltages (see clause on “relationship of test voltages to rated voltages” and Table(s) of test voltages). IS-7098 (Pt-3) follows the same framework for 66–220 kV XLPE cables (BIS Product Manual references). (BIS)

·         Range / rounding: some documents quote slightly different numbers depending on whether they use the nominal rated voltage (66/132 kV) or the standard Um value (72.5/145 kV) — and whether they round to manufacturer/utility practice. That’s why you see small spreads (e.g., 350 vs 380 kV). For procurement/test sheets use the exact numeric values called out by the purchaser/utility (or the specific clause/table in IEC 60840 / IS 7098 that applies). (BIS)

·         Accessories / joints / terminations: the impulse + power-frequency sequence and specific values for joints/terminations are covered in IEC-60840 Annexes/tables (H, G). Those accessory values can differ from cable-only values — check the relevant table when testing accessories.

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