AC Mains Power Failure Sensors

Current sensors in the form of current loops or current clamps are sensors through which a power cord is run. The loop and clamp is in two parts and attaches around the cable to be measured. The current passing through the cable is measured using induction to generate a value in Amps of the power being drawn by the connected load. The current sensor is connected to an base environment monitoring device which acts as central point for data collection. Monitoring software is used to analyse the data and trigger an alarm notification outside threshold settings.

These sensors typically plug into the local mains power supply and are connected to a monitoring base unit. When AC power source they are connected to changes state, a signal contact triggers to inform the monitoring base unit. This triggers the alarm notification.

A server room will typically have a sub-distribution board supplying the electrical circuits within the room. The circuits are protected by circuit breakers which will trip when overloaded or presented with a short-circuit. Monitoring power usage in a server room allows for capacity planning and to determine whether there is a risk of any of the circuits being overloaded. Power monitoring can be at the room, rack or even the individual socket on a power distribution unit (PDU) or socket strip.

The power distribution unit (PDU) installed should be what is termed an ‘intelligent’ PDU which features individual power outlet control. Using manufacture specific software (server or Cloud-based) should then allow individual PDU power outlets to be remotely monitored and switched ON/OFF to reboot connected devices. The local are network connection is typically Ethernet but WiFi may be an option for some PDUs or smart power sockets.

Measuring power usage in a server room or datacentre can be important for a range of factors including capacity planning, energy efficiency, billing or business continuity. Active ‘Power present’ sensors can be used to determine if power is present and signal an alarm if there is a change in state i.e. a mains power failure. Metered and Intelligent power distribution units (PDUs) can monitor power levels and usage down to individual outlet sockets. Basic power measurement information can include Volts, Amps and energy (kWh) for each individual outlet and for the PDU as a total.