Pods - PD3

Overview of the PD3
  • Low cost monitoring of key sites , power supplies and equipment
  • Monitors 3 phase inputs (or 3 voltage inputs on the same phase)
  • Monitors 3 volt free contacts
  • Detects and reports all interruptions to electricity supply
  • Reports restorations to supply
  • Reports to Central Host PC using built-in telephone line modem
  • Simple to install
  • Reprogram thresholds and settings remotely


The PD3 unit is a 3 phase version of the PD2 with additional monitoring of volt free inputs. Typical applications include the monitoring of critical power supplies and plant at unstaffed sites. Typically used by electricity utility companies to provide early warning of HV outages affecting customers fed from non-telecontrolled switchgear.

PD3 units monitor and report all interruptions to AC supply and can be used to detect transient interruptions and short duration outages. The unit also accepts volt free contacts for alarm monitoring. The PD3 has a built-in line modem connected to a telephone extension point which can be shared with a phone handset if required. Calls are made to a Central Host PC which receives, displays and logs alarms and events.

The Host Software is a bespoke application which may be used as a powerful alarm display / plant condition monitor / message forwarder/ archive. This can be a single stand-alone PC based system or a full client / server architecture with multiple communication gateways and client terminals. Mixed systems of PD2, PD3 and PD4 units reporting to the same Host PC are possible.

Voltage Monitoring

The mains voltage on each of the 3 ac inputs is measured as full wave rectified rms level, with most of the ac component removed by a high pass filter. The signal is then peak limited, potted down to set the nominal voltage for 230volts ac and high frequency filtered to remove unwanted noise. 4 voltage measurements are taken and averaged each half cycle of the mains for each input. The result is used to determine the voltage status of the mains input every 20mS, or mains half cycle.

Digital (Alarm) Inputs

The unit monitors up to 3 normally open digital units. Connections are made using screw terminals located inside the enclosure.

Operational Settings

The following settings are user set and may be reprogrammed locally using the diagnostic port or from the PC based Host Station during a routine call.
  • Nominal Voltage level
  • Over Voltage Trip threshold
  • Under Voltage Trip threshold
  • Supply Fail Trip threshold
  • Power Fail Period
  • Out of Balance Threshold
  • Host Station Telephone No.
  • Test Call Frequency

Event Detection and Reporting

The PD3 continually monitors the LV supply "looking" for deviations from the norm, which is set by a series of threshold parameters which are set by the user (see operational settings). Event logs are date and time stamped locally within the PD3. The internal real-time clock is synchronised with the Host Station clock during every contact. Event Logs are stored in non-volatile memory (EEPROM). The following events are logged by the PD3:

  • Power Failure
  • Power Restored
  • Momentary Power Outage
  • Over Voltage
  • Under Voltage
  • Out of Balance Voltage
  • Alarm Contact Trip
  • Alarm Contact Reset
  • Battery Low

All events are logged with the date and time of the event and up to 7 timers to describe the profile of the event. Most events produce immediate communication with the Host Station, however the PD3 can store up to 10 events prior to automatic download.


Event logs are communicated to the Host Station over a standard PSTN 2-wire extension line circuit. A V22 line modem is used to communicate with the PC based Host Station. Using the V22 standard ensures that the PD3 can exchange data with almost any proprietary modem installed throughout the world.

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