Partial discharge alarm system for the continuous monitoring of switchgear cabinets
To monitor partial discharges continuously in medium-voltage cells without shutting the installation down, you fit a fixed alarm system on the in-service cabinet that combines TEV, acoustic and high-frequency current sensors and raises an alert as soon as the activity exceeds a threshold. That is how the APD-ANNUNCIATOR works: each module processes 3 acoustic channels from 30 to 88 kHz and 3 high-frequency channels from 10 MHz to 1.0 GHz, both with a 40 dB dynamic range, is fixed with magnets or on a DIN rail without drilling the enclosure, and sends the alarm via led, hardware output, SCADA, web interface, SMS or e-mail.
APD-ANNUNCIATOR key data
- Measurement channels: 3 acoustic channels from 30 kHz to 88 kHz and 3 high-frequency (TEV/HF) channels from 10 MHz to 1.0 GHz per module, with a 40 dB dynamic range and up to 3 sensors connected.
- Sensors: combined TEV and contact or airborne acoustic sensors, magnetically held with an SMA connector (also in a version for installation inside the metal-clad cabinet), and 20 and 60 mm HFCT clamps with spring latch and IP66 protection for the earth conductor.
- Alarms: user-defined threshold on each channel; local led and a dedicated hardware circuit, plus remote alerting via SCADA, web interface, SMS and e-mail.
- Noise rejection: high-frequency noise mitigation algorithm based on pulse amplitude and repetition rate.
- Installation: on a DIN rail or with magnets, with the installation in service; several modules are daisy-chained with RJ45 cables that carry data and power.
- Communication and remote access: Modbus RTU and USB; password-protected web interface with user management and encrypted communications; optional LTE cellular gateway with GPS that supports up to 247 modules, keeps 12 months of data and exports to CSV.
- Physical data: 9 to 24 VDC supply and 1.2 W max., operation from -30 °C to 50 °C, IP65 with dust boots, 201 × 87 × 53 mm and 0.51 kg; CE approval.
Advantages
Simultaneous detection with several sensor technologies
The module combines TEV detection with contact or airborne acoustic detection, and also accepts high-frequency current sensors to compare technologies and reduce false positives.
Simple installation without interrupting service
Sensors are held magnetically on the cabinet surface or mounted on a DIN rail, with no need to disconnect the installation or drill the enclosure, with no supply outage.
Cascaded monitoring of several cabinets
Several modules can be daisy-chained using standard Ethernet cable, carrying data and power together, monitoring numerous distribution cabinets with minimal cabling.
Configurable local and remote alarm
Each channel accepts a user-defined threshold, with a led indicator and remote alerting via SCADA, web interface, SMS or e-mail.
Applications
- Continuous partial discharge monitoring in medium-voltage cells and in-service switchgear cabinets.
- Early detection of insulation faults in dry-type transformers and ring main units (RMUs).
- Integration with SCADA systems for trend monitoring and remote alarm generation.
- Substation installations, field applications and remote sites with limited access.
About the product
The APD-ANNUNCIATOR is mounted on a DIN rail or held with magnets on the cabinet surface. Each module accepts up to three channels and processes the acoustic and high-frequency signals, applying validation algorithms that separate real discharge activity from ambient noise.
Configuration and data retrieval are carried out via USB or through a web interface, which graphs the evolution of the activity and manages alarms. The unit includes Modbus connectivity for the installation's SCADA system and supports an optional cellular modem for remote alerting.
Available accessories: combined TEV and contact acoustic sensor, a version with airborne acoustic pick-up, high-frequency current clamps with 20 mm and 60 mm openings and IP66 protection, a portable sensor tester, and a cloud-based remote access solution.
Technical specifications
| Compatible sensors | Transient earth voltage (TEV), acoustic and high-frequency current (HFCT) |
| Input channels | 3 acoustic and 3 high-frequency channels per module |
| Acoustic bandwidth | 30 kHz to 88 kHz; 40 dB dynamic range |
| High-frequency bandwidth | 10 MHz to 1.0 GHz; 40 dB dynamic range |
| Power supply | 9 to 24 VDC; 1.2 W max. |
| Protection rating | IP65 with dust boots installed |
| Operating temperature | -30°C to 50°C |
| Weight and dimensions | 0.51 kg; 201 x 87 x 53 mm |
| Alarm threshold and reporting | Independent threshold per channel; local led and dedicated hardware output; SCADA, web interface, SMS and e-mail |
| Noise rejection | High-frequency noise mitigation based on pulse amplitude and repetition rate |
| Connectivity and approval | Modbus RTU (remote access) and USB (PC connection); CE |
Frequently asked questions
How does the APD-ANNUNCIATOR avoid false alarms caused by noise?
The APD-ANNUNCIATOR applies a high-frequency noise mitigation algorithm based on pulse amplitude and repetition rate, lets TEV, acoustic and HFCT technologies be compared on the same module, and accepts an independent alarm threshold on each channel, set to the ambient noise of each site.
How many APD-ANNUNCIATOR modules can be managed remotely?
The optional LTE cellular gateway connects a chain of up to 247 APD-ANNUNCIATOR modules to the internet, with GPS positioning, 12 months of stored data, CSV export and e-mail alarms from a password-protected web interface.
Which sensor technologies does the unit combine?
It combines TEV detection, contact or airborne acoustic detection and, optionally, high-frequency current sensors, with up to three channels of each type per module.
Does the installation need to be shut down to fit it?
No. Sensors are fixed magnetically or on a DIN rail on the in-service cabinet, with no need to disconnect the installation or drill the enclosure.
Can several cabinets be monitored at the same time?
Yes, several modules can be daisy-chained using Ethernet cable, carrying data and power together, with minimal cabling.
How are alarms received?
Through a local led indicator, and remotely via SCADA, web interface, SMS or e-mail, according to each channel's threshold.
What protection rating does the unit offer?
IP65 with the dust boots installed, with an operating temperature range of -30°C to 50°C.
