Why Singapore Needs PD Monitoring
Singapore operates one of the most reliable electricity grids in the world, but its reliability depends on assets that rarely get a second look until they fail. The network is predominantly underground, the load density is extreme, and data centres — the country’s fastest-growing power consumers — cannot tolerate unplanned outages. Partial discharge (PD) is the earliest measurable sign of insulation deterioration in switchgear, transformers, cables and GIS. Detecting it early is the difference between a planned maintenance action and a forced shutdown.
Three conditions make PD monitoring especially relevant in Singapore:
- Underground-dominated distribution: buried cable joints and terminations are exposed to moisture ingress and load cycling, classic PD triggers.
- High humidity and condensation: tropical climate accelerates tracking and surface discharge in air-insulated switchgear.
- Data centre density: UPS systems, MV switchboards and backup generation operate continuously; any internal flashover has outsized business impact.
Key Applications in Singapore
Data Centre Switchgear and UPS
Data centre MV and LV switchboards are prime candidates for online monitoring. TEV (transient earth voltage) and ultrasonic sensors can be permanently fitted to switchgear panels, or used as a portable survey tool during planned maintenance windows. For facilities where downtime is measured in minutes, retrofitting a small online PD monitoring system to critical switchboards provides continuous visibility without requiring outages.
Underground Cable Networks
Distribution cable joints are the most failure-prone component in underground networks. HFCT (high-frequency current transformer) sensors clamped around cable earth leads can monitor PD activity online, while oscillating wave (OWTS) testing provides a more thorough assessment during planned outages. A combined strategy — annual OWTS for critical feeders and continuous HFCT monitoring for the highest-risk circuits — is a practical model for Singapore’s cable-heavy network.
Substation GIS and RMU
For GIS bays, UHF sensors are the established method: they offer high sensitivity and strong noise rejection, and can be installed via existing inspection ports or dielectric windows. Ring main units (RMU) in residential and commercial supply chains can be monitored with compact 3-in-1 sensors combining TEV, AE and temperature/humidity measurement, which also helps correlate PD activity with environmental conditions.
Choosing the Right PD Monitoring Approach
Portable Testing First
If you are building a programme from zero, start with a portable PD detector for TEV, ultrasonic and HFCT surveys. This establishes a baseline across your network and identifies the panels, joints and bays that need attention, at a fraction of the cost of full online deployment.
Online Monitoring Where Risk Is Highest
Permanent sensors earn their cost where failure is most expensive: data centre switchboards, critical substation GIS, and heavily loaded cable feeders. Start with a handful of high-risk locations, validate the data for a quarter, then expand.
Data Integration Matters
PD data becomes actionable when it reaches the people who maintain the network. Choose systems that export to standard protocols (Modbus, IEC 61850 where applicable) or provide clear cloud dashboards with alarm thresholds, so the monitoring system does not become another silo of data.
FAQ
What is the difference between TEV and UHF PD monitoring?
TEV measures transient earth voltages on the surface of air-insulated switchgear and is the quickest method for panel-level surveys. UHF is used mainly for GIS, where the metallic enclosure contains the signal; it offers high sensitivity and better immunity to external noise. Many utilities use both: TEV for air-insulated equipment, UHF for GIS bays.
Can PD monitoring be retrofitted without an outage?
Yes for most online sensors. TEV and AE sensors are surface-mounted; HFCT clamps around an existing earth conductor; UHF sensors can often be inserted through inspection ports or dielectric windows on GIS without de-energising the bay. OWTS and other offline methods, by contrast, require a planned outage.
How often should cable joints be tested?
A common starting point is annual OWTS testing for critical feeders, with continuous HFCT monitoring on the highest-risk circuits. For lower-risk feeders, a 2-3 year cycle is typical. Trending results year over year matters more than the absolute measurement.
Does humidity affect PD measurement accuracy?
High humidity raises background noise and can cause surface discharge that mimics real insulation defects. That is why combining PD measurement with temperature and humidity data — as the 3-in-1 sensor does — helps distinguish environmental effects from genuine insulation problems.