High Voltage Cable Services

Ensure Reliability of Your Critical Underground Distribution

PE-licensed engineers

Capable of being licensed in all 50 states

NETA-certified technicians

ANSI/NETA ATS and MTS testing

IEEE, NFPA, and InterNATIONAL ETA members

Active in the standards your AHJ cites

The Hidden Vulnerability in Your Power System

High voltage cables represent 60% of unplanned substation outages, yet they're the least visible component. Cable failures occur without warning, causing catastrophic equipment damage and extended downtime averaging 48-96 hours.

Proactive cable testing and diagnostics detect developing insulation problems years before failure, enabling planned replacement and preventing emergency outages that cost facilities $50K-$500K+ per event.

What are High Voltage Cable Services?

High voltage cable services encompass testing, diagnostics, maintenance, and repair of medium voltage (5-35kV) and high voltage cable systems. These services include:

Diagnostic Testing

VLF hipot, tan delta, partial discharge testing

Fault Location

TDR, impulse, and bridge methods for pinpointing faults

Preventive Maintenance

Scheduled testing and condition assessments

Emergency Repairs

24/7 fault location and cable replacement

Services cover all cable types: XLPE, EPR, PILC (paper-insulated lead covered), shielded, non-shielded, and applications including substation feeders, underground distribution, and industrial plant systems.

Why This Service is Critical

Catastrophic Failure Prevention

Cable failures are explosive events. Insulation breakdown creates arcs that vaporize conductor material, generating pressures exceeding 10,000 psi. The resulting explosion destroys adjacent cables, damages terminations, and can rupture concrete vaults. Repair requires excavation, emergency cable procurement, and multi-day outages.

Real Example:

Hospital's 30-year-old 15kV feeder cable failed during peak load on a summer afternoon. The explosion destroyed three adjacent cables in the vault and damaged the switchgear termination compartment. Emergency generators sustained critical loads, but entire facility operated at reduced capacity for 11 days during repair. Total cost: $780K including cable ($45K), emergency labor ($120K), switchgear repairs ($85K), and generator fuel/rentals ($530K). Annual cable testing: $8K.

Predictive Maintenance Capability

Modern diagnostic testing identifies degrading insulation before failure. Tan delta and partial discharge measurements detect water treeing, insulation aging, and defective terminations. Trending test results over years provides clear warning when replacement is needed, enabling planned outages during favorable conditions versus emergency response.

Asset Life Extension

Cable systems properly maintained and monitored operate reliably for 40-50 years. Cables without condition monitoring often fail at 20-30 years. With replacement costs of $100-$500 per foot installed, life extension through testing and maintenance generates enormous ROI.

Rapid Fault Location

When cables fail, every hour matters. Professional fault location services pinpoint failures within feet using TDR and impulse methods, minimizing excavation and repair time. Without these services, facilities resort to trial-and-error excavation that extends outages days longer and costs 5-10x more.

Common Problems This Service Solves

1. Water Treeing and Moisture Intrusion

Water penetrates cable insulation through damaged jackets, defective splices, or terminations. Once inside, moisture creates conductive "trees" that grow through insulation over years. Tan delta testing detects elevated moisture before catastrophic breakdown. Early detection enables termination replacement or cable section replacement before complete failure.

2. Insulation Aging and Thermal Degradation

Insulation degrades from electrical stress, thermal cycling, and chemical reactions. XLPE cables experience oxidation; PILC cables suffer dielectric breakdown. VLF hipot and partial discharge testing reveal degradation severity. Condition-based replacement prevents sudden failures and enables budgeting for planned upgrades.

3. Termination and Splice Failures

Poor installation, moisture ingress, or material degradation cause terminations and splices to fail. These failures often occur at stress cones where electric fields concentrate. Partial discharge testing identifies defective terminations before failure. Preventive replacement of failing terminations costs $5K-$15K; emergency cable replacement costs $100K-$500K.

4. Shield Grounding Problems

Improper shield grounding causes circulating currents that overheat cables, or floating shields that lead to dangerous voltage rise. Shield continuity testing and induced voltage measurements identify grounding defects. Correcting grounding issues prevents thermal damage and personnel safety hazards.

5. Unknown Fault Locations

When cables fail without proper fault location, repair becomes guesswork involving extensive excavation. Professional TDR and impulse testing pinpoints faults within 3-10 feet accuracy, even in complex routes with multiple bends and splices. This eliminates exploratory digging that damages infrastructure and extends outages.

Request a cable testing and diagnostic scope

Send a list of your circuits (voltage class, length, splice count, age) or your last test reports. ClarkTE returns a written test plan covering VLF, tan delta, partial discharge, and TDR — with a fixed fee and outage window — within one business day.

When Should You Schedule This Service?

Immediate Service Indicators

• Cable fault or complete failure
• Partial discharge activity detected (crackling sounds)
• Recent dig-ins or mechanical damage
• Moisture found in termination or splice
• Failed insulation resistance tests
• Previous test results showing deteriorating trends
• Cables 25+ years old without recent testing
• Known PILC cables in service

Recommended Testing Schedule

• New installations: Acceptance testing per NETA ATS
• 5-10 years: VLF hipot and insulation resistance
• Critical circuits 15+ years: Annual tan delta and PD testing
• PILC cables: Annual testing after 20 years
• After events: Testing following faults, overvoltages, or dig-ins

Best Practice: Implement condition-based monitoring for critical feeders. Annual testing establishes trends that predict failures 2-5 years in advance.

What to Expect During the Service

Phase 1: Pre-Test Planning (1-2 weeks before)

• Review cable records, drawings, and previous test results
• Develop test plan based on cable age, type, and history
• Coordinate outage scheduling and isolation requirements
• Prepare specialized test equipment and safety protocols

Phase 2: Visual Inspection (Day 1, 2-4 hours)

• De-energization, isolation, and grounding verification
• Termination inspection for tracking, contamination, moisture
• Shield continuity and grounding verification
• Documentation with thermal imaging

Phase 3: Diagnostic Testing (Day 1-2, 4-8 hours per circuit)

• Insulation resistance (megohm) testing
• VLF (very low frequency) hipot testing at 2-3x operating voltage
• Tan delta (dissipation factor) measurements
• Partial discharge testing during VLF application
• Shield resistance and induced voltage testing
• Phasing verification

Phase 4: Analysis & Reporting (3-5 days after testing)

• Detailed test result analysis and trending
• Condition assessment with remaining life estimates
• Prioritized recommendations for repairs or replacement
• NETA-certified test reports with acceptance criteria
• Budget planning guidance for capital improvements

Typical Duration: Complete diagnostic testing of a 3-phase cable circuit requires 6-12 hours depending on cable length and accessibility. Fault location services typically complete within 4-8 hours.

ROI & Business Value

Cost Avoidance

$100K-$500K+

Emergency cable failure and repair costs

$5K-$15K

Comprehensive diagnostic testing per circuit

10-50x

ROI from preventing ONE emergency failure

Operational Benefits

• Planned replacement during favorable conditions
• 2-5 year advance warning of impending failures
• Reduced emergency response costs (10x savings)
• Elimination of exploratory excavation
• Extended cable life through condition monitoring
• Insurance documentation for premium reductions
• Enhanced system reliability and uptime

Industry Standards & Compliance

ANSI/NETA ATS & MTS: Acceptance and Maintenance Testing

Defines test procedures, voltage levels, and acceptance criteria for cable systems including VLF hipot, tan delta, and partial discharge testing.

IEEE 400 Series: Cable Testing Standards

IEEE 400.2 (field testing), 400.3 (partial discharge), and 400.4 (VLF testing) provide comprehensive guidance on cable diagnostic methods and interpretation.