Even under normal conditions, it is worth making sure that electrical equipment receives a stable voltage. But now, when power outages occur on a regular basis, it becomes even more important. In the previous article "There is no magic in energy", we have already discussed in detail how to ensure the energy independence of an apartment or house during blackouts - now it is worth supplementing the story with a description of what can be done against power surges, which pose a serious threat to household appliances.
The standard voltage in Ukraine is set by DSTU EN 50160:2014 "Characteristics of the voltage of power supply in general-purpose electrical networks". It states the following:
The standard rated voltage Un for general-purpose low-voltage networks is 220 V between the phase and neutral conductors or between the phase conductors:
- for three-phase four-wire networks: Vn = 220 V between phase and neutral conductor;
- for three-phase three-wire networks: Vn = 220 V between the phase conductors.
The voltage change should not exceed ±10% of the rated voltage.
Accordingly, the normal range is 198-242 V, and this is usually the case. Voltage surges outside the normal range occur for various reasons. During normal operation and in places where the power grid itself is reliable (not as it sometimes is in rural areas), serious surges are an excess. For example, due to a short circuit, or damage to the insulation, or a lightning strike... In other words, it's already an emergency.
A diligent householder will try to protect their property from such cases, but it's like life insurance - a procedure that not everyone cares about. But now, when there is a blackout, the situation is different and everyone needs to worry. Because every time the grid is turned off and on, there is a risk of a power surge, as well as sudden changes in load (when consumers turn on many appliances at the same time), as well as grid overload... Of course, high voltage in the network is a bigger problem than low voltage, so overvoltage protection is more common than undervoltage protection - but there are exceptions.
The entire existing system of protection against power surges is deeply tiered, starting from the national level and ending with a circuit breaker (or "automat") near each modern meter at each consumer. There are both state standards and instructions from the National Energy and Utilities Regulatory Commission (NERC). But this is not enough. There are several tools that can help save the equipment from power surges, and, just like at the higher level, it is advisable to combine them to achieve the best result.
Voltage relay for DIN rail mountingThe voltage relay serves as the main protection device in the home. If the voltage deviates from the normal range, the relay automatically disconnects the equipment from the mains. It is installed on the input cable in front of all appliances, providing the first line of protection. Surge protective relays have several advantages over conventional circuit breakers. They are specifically designed for overvoltage protection, not just overcurrent protection. The relays have more precise and customizable trip parameters to ensure optimal protection. They protect against various types of power system faults, not just current protection. Modern relays are equipped with functions for diagnosing the state of the power grid, which helps to identify problems in time. In addition, protection relays have a more reliable design, designed for long-term operation in difficult conditions. Surge protective device A surge protective device (SPD, also known as an arrester, or lightning protection device) is also installed at the power input. Surge protectors protect against powerful and rapid voltage surges, for example, when lightning strikes. They are capable of handling serious power, enough to power an entire house. Plug-in voltage relay Typical surge protector By the way, it is advisable to plug these powerful appliances into sockets, not power strips. But for computer or audio-video equipment, the best simple protection is a surge protector, which is often confused with an extension cord. The difference is simple: an extension cord is literally just a "power strip with an extra wire," while a surge protector has a built-in protection system in the form of a metal oxide varistor (MOV). This component has a three-layer structure: metal oxide material is located in the middle, and on both sides it is connected to the power line and ground through semiconductors. MOV works on a simple but effective principle. Under normal conditions, it has a high resistance and does not affect the current flow. However, when the voltage rises sharply, the MOV resistance decreases significantly. In this state, it quickly diverts the excess current to ground, protecting the connected devices from potential damage. In this way, the MOV acts as a circuit breaker that activates only at dangerous voltage levels and protects all consumers connected to the surge protector's outlets. When buying a surge protector, it is important not to confuse it with an extension cord - sometimes extension cords also have a power button and an LED operation indicator, but they do not provide protection! Pulse stabilizer in portable version (500 W) In order to avoid the problem with the surge itself, whether for a specific consumer or for the entire building, you can use inverter voltage stabilizers that provide a stable current supply by adjusting the voltage in real time. They reliably protect equipment from voltage surges by constantly adapting to changes in the power grid. Accordingly, the stabilizer itself still needs the above-described "input" protection, but the output devices simply receive a voltage as close to the standard 220 V as possible. This way, for example, you can solve the problem with charging Bluetti stations, which are known for their demanding voltage. Of course, the more powerful a stabilizer is, the larger it is and the more expensive it is. Pulse stabilizer in stationary version It's worth recalling that a lot of equipment can operate in the range of 100 to 240 V because it is still powered by low voltage (usually 5 to 20 V) and direct current. So the power supply of a smartphone or laptop can easily consume even 100 V from the mains and still provide the necessary output parameters, thus working both as a transformer and a stabilizer. It also allows the same chargers to be used worldwide regardless of the local voltage standard. Accordingly, they still need surge protection, but almost no critical voltage drop below the European 220-volt standard. But more powerful household appliances of the American standard (110 V), if imported to Ukraine, require an external transformer in our conditions, which will convert 220 V from the mains to the required 110 V. And it is also advisable to protect such a transformer from power surges, because it delivers a banal 50% of the input voltage without stabilizing it. UPS has many forms Finally, uninterruptible power supplies (UPS) are also suitable not only for power supply during short-term power outages, but also for voltage stabilization. However, they are themselves vulnerable to ultra-high voltage surges, so it is important to provide additional protection in the electrical panel. The choice of UPS is beyond the scope of this article, but this functionality is worth noting. *** Remember that the correct selection and installation of protective devices requires taking into account the specifics of your electrical network and equipment. In complex cases, it is recommended to contact an electrical specialist for professional advice and assistance in choosing the best solution. High-quality power surge protection is an investment in the durability and safety of your household appliances and electronic devices, even in peacetime, and is now an almost mandatory requirement if you do not want to lose your valuable equipment.
