Small size – big consequences
Although relatively small, voltage dips can cause major problems. Production shutdowns with all related costs, for example, such as loss of production, waste of raw materials and overtime. In determining the costs of an electrical fault caused by a voltage dip, other aspects come into play, too. Customer satisfaction plays a role, as do safety risks. These additional aspects are often difficult to measure, but certainly ought to be taken into account. By detecting, analyzing and solving voltage dips, unnecessary costs and problems can be prevented.
Costs that can be associated with a voltage dip
When we talk about the costs that can be associated with a voltage dip, we can distinguish between direct and indirect ‘costs’. If we only look at the direct costs, these can already lead to considerable amounts. We should certainly not forget the indirect ‘costs’, it is better to speak here of indirect damage. This indirect damage can also have a major impact on both short and long term business results.
– Loss of production
– Loss of raw material
– Personnel costs
– Damage to equipment
Financial loss varies per sector
Out of all Power Quality characteristics, voltage dips result in the greatest financial and economical damage. However, the average cost of a voltage dip may differ for each sector. In the pharmaceutical (fine chemistry) and semiconductor industries, the costs per voltage dip are significantly higher than in, for example, the food or textile industry. Sometimes, this difference can go up to a factor ten. The requirement to register and collect voltage dips varies across sectors. The higher the cost per dip, the greater the need for a solution.
Additional negative effects (= indirect damage)
– Decreased customer satisfaction (e.g. due to longer delivery times)
– Safety risks (due to sudden failing of equipment)
– Unfavourable impact on sustainability (due to extra production hours and loss of production and raw material)
Greatest risks with sensitive equipment
Voltage dips may have a variety of consequences. Devices and machines might stop working and control processes may be disrupted. Sensitive equipment, such as PLC’s, frequency drives and contactors, are particularly quickly affected by voltage dips. This type of equipment is often found in a production environment, where it is central to the production process. A dip can bring an entire factory to a sudden standstill, resulting in vast direct and indirect damage. The magnitude of the effects of voltage dips strongly depends on the level of the voltage drop, the duration of the voltage dip and the dip frequency.
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Definition of voltage dips
A voltage dip is a sudden brief dip in voltage of at least 10%. According to NEN-EN 50160 ‘Voltage characteristics in public electricity networks’, a voltage dip is:
“[…] a sudden reduction of the voltage, to a value between 90% and 1% of the voltage, followed by a recovery after a short period of time. The dip duration is between 10ms and 1 minute and the depth of the dip is the difference between the minimum effective value of the voltage during the dip and the agreed value. Usually, the dip duration is a few seconds. If a dip lasts longer than 1 minute, we no longer speak of a voltage dip, but a break.”
What causes voltage dips?
Voltage dips are generally caused by electrical breakdowns. These electrical breakdowns can occur in your own installation, as well in the electricity network.
Electrical breakdowns in the electricity network can be caused by
Electrical breakdowns can occur in high, medium or low voltage. However, electrical breakdowns in low voltage are very rare.
Inrush currents / switching on of large loads
Inrush currents are a well-known cause of voltage dips. When switching on large loads, such as transformers and large electrical motors, a large amount of energy is immediately required from the electrical installation. This may cause errors in the installation. A large current flows through the cable towards the load, which causes a voltage drop. Depending on its duration and depth, this voltage drop can be seen as a dip.
Standards concerning voltage dips
With regard to standards, we can be brief: voltage dips are not yet standardized in the network code. This means that the network operator cannot be held responsible at present. The standard is currently in the making. In the near future, there will be more clarity from the network code about the standards and responsibilities regarding voltage dips.
An electrical installation can be made immune to voltage dips. To achieve this, a number of steps need to be made in order to implement the right solution.
The first and most important step is to provide insight into the voltage dips. This can be realized with long-term measurement (1 to 4 weeks) and/or through (permanent) installation of appropriate Power Quality analyzers at various (predetermined) points in the electrical installation. In order to achieve the best possible solutions and arrive at a correct plan, it is important that the obtained data is analyzed using the right kind of professional knowledge.