Voltage drops can lead to the failure of computer systems, and have major cost implications. Working on the basis that the first step towards dealing with them is identifying them, Janitza electronics has developed a wide range of power quality analysers that pick up on any short-term interruptions or voltage drops.
The commercial effects of voltage drops are seriously underestimated. Voltage drops can lead to the drop-out of production processes, and to product or process quality problems. Such voltage drops arise much more frequently than interruptions; however, many cases go unidentified.
According to the European standard EN 50160, a voltage drop is a sudden lowering of the effective voltage value to a value of between 1% and 90% of the stipulated nominal value, followed by the immediate recovery of this voltage. The duration of a voltage drop lies between a half-period (10ms with 50Hz grids) and one minute.
Starting currents: a well-known cause of voltage drops is the starting or inrush current for capacitors, motors and other devices. The current increases briefly when the motor starts up, and the inrush current leads to a voltage drop across the impedances Z and Z1. However, it leads to a smaller voltage drop at the low-voltage bus bar (drop zone 1) and a somewhat larger voltage drop behind impedance Z1 (drop zone 2). Typical solutions would be adequate starting equipment, such as capacitor contactors for power-factor correction or soft starters for motors.
Short circuits in the low voltage network: a very high current flows in the event of a short circuit in the low-voltage network. The peak of the short-circuit current depends on the value of the impedances Z and Z3. The short circuit current causes a voltage drop across impedance Z, whereby the voltage at the low-voltage main distribution bus bar collapses briefly.
Voltage drops can lead to the failure of computer systems, programmable logic controller (PLC) systems and frequency converters. With critical processes, just a single voltage drop can result in high costs; continuous processes are particularly impacted. Examples include injection-moulding processes, extrusion processes, and cable and semiconductor factories.
The costs of a voltage drop comprise:
Sometimes, processes run in unmanned areas in which voltage drops are not immediately noticed. An injection-moulding machine, for example, could come to a complete standstill without anyone noticing.
IT systems are particularly susceptible to voltage drops and voltage interruptions. This means that all processes that are controlled by microprocessors are vulnerable to this type of interference, including PLC systems, frequency converters, machine controllers, servers at data centres and PCs.
Janitza electronics offers a wide range of power quality (PQ) analysers that are able to identify short-term interruptions and voltage drops. The UMG 604 power analyser continuously monitors more than 800 electrical and PQ parameters. All channels are sampled 20,000 times a second, enabling short-term voltage interruptions and drops to be signalled and recorded. Records can be sent by email if required, while the measurement device has a web browser that can be used to call up the most important parameters directly.
The Janitza measurement devices for identifying short-term interruptions are:
The GridVis Basic licence is provided along with the Janitza measurement devices free of charge. This software package enables the read-out of real-time measurement values; retrieval of historical measurement data in files and graphics; analysis of short-term interruptions, transients and voltage drops; and the generation of complete EN 50160 reports and other PQ reports.
Some voltage drops can be reduced by reworking the electrical infrastructure. The first step, however, is always identification and documentation. Janitza offers complete solutions that continuously monitor and analyse complete operating processes sustainably and securely.
