Direct Answer

PD (partial discharge) sensors have arrived, but the construction crew is unsure how to install them so the measurement is accurate. The answer: three installation steps — choose the coupling method by the detection technique (UHF in-built / TEV on the cabinet wall / ultrasonic clip-on); place measurement points near high-discharge areas such as the busbar chamber and cable chamber; measure the background noise once before commissioning as the baseline; after installation, perform a no-load verification to confirm the sensor signal path is normal before putting it into service.

At one industrial park's 10kV switchgear PD monitoring: TEV sensors were attached to the cabinet wall (busbar and cable chamber areas), UHF was in-built near the busbar, ultrasonic sensors were clip-mounted on cabinet gaps; background noise was measured before commissioning (TEV baseline 12dBmV); a no-load verification confirmed each signal path. Three months after commissioning, cable-chamber TEV rose from 12dBmV to 28dBmV (alarm); a power-off inspection confirmed cable-termination discharge — the signal was trustworthy. Installation core: coupling method, measurement-point location, and baseline verification — install it right, and the measurement is accurate.

Because:

  • The coupling method determines "whether it can receive": UHF in-built / TEV wall-mounted / ultrasonic clip-on each has its applicable scope;
  • The measurement-point location determines "what it receives": busbar and cable chambers are high-discharge areas;
  • The background-noise baseline determines the "judgment reference": measure once before commissioning so later changes have a benchmark;
  • The no-load verification determines "whether the signal is trustworthy": only put it into service after the signal path is confirmed.

Key insight: "install in the right place, measure the right baseline, verify the right path" — the three essentials of reliable PD monitoring. Location + baseline + verification — trustworthy data starts with standardized installation.

At one plant, TEV sensors were mounted at the cabinet bottom (far from the cable chamber): after commissioning the signal was weak with heavy interference, and the data was untrustworthy. Rectification: moved to the busbar/cable-chamber area, re-measured the background-noise baseline, and passed no-load verification. Lesson: a wrong location means inaccurate measurement — place points near high-discharge areas and measure the baseline before commissioning.

1. Coupling Methods of Each Sensor

Step one: how to choose the coupling method.

UHF in-built:

  • Principle: built-in antenna receives high-frequency electromagnetic waves (300MHz–3GHz);
  • Applicable: internal discharge detection in switchgear/transformers;
  • Installation: cabinet opening or dedicated interface, near the busbar;
  • Characteristics: high sensitivity, good location capability;
  • Note: confirm the opening with the cabinet manufacturer (do not damage insulation).

TEV wall-mounted:

  • Principle: transient earth voltage (propagates along the cabinet surface);
  • Applicable: external detection on switchgear (no opening);
  • Installation: attached to the cabinet wall (busbar/cable-chamber areas);
  • Characteristics: simple installation, no cabinet modification;
  • Note: firm adhesion (silica gel/double-sided tape), avoid grounding interference.

Ultrasonic clip-on:

  • Principle: receives ultrasonic signals (20kHz–200kHz);
  • Applicable: cabinet gaps/insulators/bushing through-walls;
  • Installation: clipped on cabinet gaps or sensor seats;
  • Characteristics: EMI-immune, directional;
  • Note: firm clipping, avoid vibration interference.

Selection comparison:

  • Opening allowed + highest sensitivity: UHF in-built;
  • No cabinet modification + surface detection: TEV wall-mounted;
  • Local gaps + EMI immunity: ultrasonic clip-on;
  • Multi-method combination: UHF + TEV (covering internal + surface).

Key insight: choose the coupling method by detection technique and on-site conditions. UHF when opening is allowed, TEV when not modifying the cabinet, ultrasonic for local gaps — combinations give broader coverage.

2. Measurement-Point Location

Step two: where to install.

High-discharge areas:

  • Busbar chamber: busbar joints (thermal expansion/loosening discharge);
  • Cable chamber: cable terminations/joints (weak insulation points);
  • Breaker chamber: contacts/arc chamber (operation wear);
  • Bushing through-walls: bushing roots (concentrated electric field).

Layout principles:

  • Busbar chamber: at least 1 point per busbar section;
  • Cable chamber: 1 point per outgoing bay (near cable terminations);
  • Breaker: near contacts (optional, frequent-operation locations);
  • Space-limited: prioritize busbar + cable chambers (highest discharge areas).

Notes:

  • Avoid grounded metal (shields the signal);
  • Avoid strong EMI sources (be cautious with ultrasonic near large-current busbars);
  • Keep the cabinet surface clean (firm adhesion);
  • Record point numbers and locations (installation records).

Example:

  • 10kV incoming cabinet: busbar TEV + UHF, cable-chamber TEV;
  • Feeder cabinet: cable-chamber TEV (per bay);
  • Transformer cabinet: body ultrasonic + oil temperature (combined).

Key insight: place points in high-discharge areas. Busbar + cable chambers first, avoiding interference sources — a right location gives the signal value.

3. Background-Noise Baseline Measurement

Step three: how to measure the baseline.

Why measure a baseline:

  • On-site noise (corona/interference/environment) affects interpretation;
  • Without a baseline you cannot distinguish discharge signals from background noise;
  • The baseline is the zero point for later trend judgment.

Measurement method:

  • Measure once before commissioning (when no discharge interference);
  • Record each point separately (noise differs per point);
  • Record continuously (take the mean of short-term fluctuation);
  • Record operating conditions (load/weather/neighbor equipment states).

Baseline content:

  • TEV amplitude (dBmV) and pulse count;
  • UHF signal strength (dBm) and event count;
  • Ultrasonic amplitude (dB) and event count;
  • Per-point reference-value table (archived).

Notes:

  • Note areas with high environmental noise (reference for later interpretation);
  • Re-measure the baseline periodically after commissioning (season/condition changes);
  • For abnormal baseline (sudden rise), investigate the interference source first.

Key insight: the baseline is the zero point of judgment. Measure before commissioning, record point by point, archive with notes — later changes have a reference.

4. No-Load Signal Verification

Step four: how to confirm the installation is correct.

Verification purpose:

  • Confirm the sensor signal path is normal;
  • Exclude installation errors (poor contact/wrong wiring);
  • Verify data is uploaded to the platform correctly.

Verification method:

  • Measure each point at no-load/low load;
  • Compare with the baseline (should be close to baseline values);
  • Check data upload (visible on the platform);
  • Troubleshoot installation on abnormal signals (no signal/sudden change).

Common-problem troubleshooting:

  • No signal: wiring/sensor fault/location shielding;
  • Weak signal: loose adhesion/wrong location;
  • Sudden signal change: interference/loose contact;
  • Data not uploading: communication/configuration issue.

Pass criteria:

  • Each point uploads normally;
  • Amplitude close to baseline (no obvious anomaly);
  • Interference sources identified and recorded;
  • Installation records and labels complete.

Key insight: no-load verification is the installation acceptance. Path normal, data uploaded, baseline compared — only then put it into service.

5. Installation Records and Labels

Step five: how to leave a standardized trail.

Record content:

  • Point number and location description;
  • Sensor model and coupling method;
  • Background-noise baseline value;
  • Installation date and crew;
  • Verification result and notes.

Label requirements:

  • Paste point labels on the cabinet (number + type);
  • Corresponding system-point configuration (platform sync);
  • Archive records (engineering documents + maintenance ledger).

Follow-up management:

  • Baseline re-measurement cycle (quarterly/semi-annual or on condition changes);
  • Abnormal-signal records (compared with installation records);
  • Update records on retrofit/point moves;
  • Sensor-life management (replacement cycle).

Key insight: records and labels are the guarantee of traceability. Number + baseline + verification — complete data, evidence-based operation and interpretation.

6. Product Landing: Digital Electrical Intelligent Supervision System

FEXLINK products land PD installation:

  • Multi-sensor access: unified access for UHF/TEV/ultrasonic;
  • Point management: online management of numbers/locations/baselines;
  • Trend interpretation: PD trends referenced to baselines;
  • Verification tooling: commissioning checks and data validation.

Design principle in one sentence: "install right, measure accurately, verify passed." Coupling method + points + baseline + verification — trustworthy PD data.

Pre/post-installation checklists:

  • Before: confirm cabinet structure and opening plan (UHF); prepare silica gel/double-sided tape (TEV); confirm clip locations (ultrasonic);
  • During: place points per "busbar + cable chambers first"; firm adhesion (silica gel/stable clipping); avoid grounded metal and strong EMI sources;
  • After: measure the background-noise baseline point by point (record conditions); no-load verify signal paths (compare baseline); confirm data upload to the platform; paste point labels and archive records.

7. Common Installation Misconceptions

  1. Random placement: sensors at the cabinet bottom. Consequence: weak signal/heavy interference. Correct: near busbar/cable-chamber high-discharge areas.
  2. No baseline: reading signals immediately after commissioning. Consequence: cannot distinguish discharge from noise. Correct: measure background noise before commissioning as the baseline.
  3. No no-load verification: leaving right after installation. Consequence: poor contact/wrong wiring unknown. Correct: verify the signal path at no load.
  4. Loose adhesion: TEV sensors loosely attached. Consequence: signal attenuation/instability. Correct: silica gel + firm adhesion.
  5. No records or labels: not registered after installation. Consequence: no reference for later interpretation/points hard to find. Correct: archive number + baseline + verification records.

Scope and Limitations

This article provides an on-site installation guide for switchgear PD sensors (coupling methods, measurement-point locations, background-noise baselines, no-load verification, installation records) for PD monitoring on 10kV and above switchgear. Specific installation plans must be determined by cabinet structure, on-site space, and manufacturer requirements; cabinet openings must be confirmed with the cabinet manufacturer (do not damage insulation); installation and verification must be performed by qualified personnel per procedures. All cases are anonymized (a certain industrial park/a certain plant) and do not refer to any specific customer.