The acceptance test for medium- and high-voltage shielded cables is a factory and field protocol that verifies insulation integrity and jacket condition before a new or reconditioned cable is placed into service. The test encompasses dielectric measurements (most commonly an insulation-resistance or DC-withstand check), a shield-continuity resistance measurement to confirm the metallic shield forms an unbroken path to ground, a jacket-integrity check at a specified test voltage held for one minute to confirm the outer covering is free of damage or defects, and a complete identification of the cable's rated voltage (phase-to-phase in kV), insulation level (100 percent, 133 percent, or 173 percent per NETA ATS-2025 Table 100.6.1), cable type and construction (extruded or laminated dielectric), manufacturer, insulation material, and the circuit or feeder designation. NETA ATS-2025 section 7.3.3 governs the acceptance requirements.
A shielded medium- or high-voltage cable carries high electrical stress between its conductors and ground, and between its phases in a three-phase circuit. Any weakness in the insulation - a void, a contaminated or fractured layer, moisture intrusion, or external damage to the jacket that exposes the shield or insulation to the environment - can initiate an internal failure once voltage is applied. Confirming jacket integrity and insulation soundness before energization guards against undetected defects that could lead to an in-service fault, sustained outages, or equipment damage downstream. Field testing at installation also verifies that the cable was not damaged during shipment, handling, or termination preparation.
Acceptance: before a new cable installation is first energized, or after a reconditioned section is returned to service. The test is typically run in the factory on representative samples of cable from a given manufacturing lot, and again in the field at the job site after the cable has been terminated and before it is switched in. The test may be repeated on a time interval (annually or biannually on cables already in service, depending on the owner's program), or triggered by an event such as a repair, retermination, or a fault that created a risk of insulation damage.
With the cable de-energized, isolated from the circuit, and grounded per safety procedures, all connected apparatus (transformers, switchgear, cable terminations) are either disconnected or bypassed so the cable stands electrically isolated for testing. The tester applies the specified test voltage to the jacket for one minute and monitors for breakdown, leakage, or arcing. For insulation resistance or DC-withstand measurements, the same isolation applies: one conductor is energized while the others and the shield are grounded, the voltage is ramped to the specified test level, held steady for the duration, then reduced to zero before any leads are moved or disconnected, all of it recorded on the test instrument or chart to document the cable's behavior under stress. Shield continuity is checked separately by measuring the resistance of the shield conductor end-to-end with a low-resistance ohmmeter; a discontinuous or high-resistance shield is investigated before the cable is accepted.
For each cable section or feeder: the manufacturer, cable type, dielectric construction type (extruded or laminated), insulation material, rated voltage in kV phase-to-phase, assigned insulation level (100 percent, 133 percent, or 173 percent per NETA ATS-2025 Table 100.6.1), test voltage applied, test duration, the jacket-integrity result (pass or fail), insulation-resistance or DC-withstand reading (in megohms or kV as applicable), the shield-continuity resistance reading in ohms, any arcing or breakdown observed, ambient temperature, test-instrument identification (make, model, serial, calibration due date), circuit or feeder identifier, and the as-found and as-left cable termination or isolation condition.
NETA ATS-2025 section 7.3.3 sets the jacket-integrity test voltage and the pass-fail criterion for insulation resistance or DC-withstand based on the cable's rated voltage and insulation level. A jacket must withstand the specified one-minute test voltage without breakdown, and insulation resistance must exceed a minimum threshold that scales with the cable's voltage class per NETA ATS-2025 Table 100.1 - though the standard cautions that manufacturer's published data, not the table alone, governs the definitive minimum once the cable's conductor and insulation geometry, temperature, and overall length are accounted for. The shield must exhibit continuity; a measured resistance greater than ten ohms per 1000 feet of cable is investigated before the cable is accepted. A result below the applicable threshold, or any visible damage, arc marks, or breakdown during the test, bars the cable from being energized until the defect is investigated and either repaired or the cable section is replaced. See the purchased standard for the complete voltage-class and insulation-level table and the numeric thresholds.
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