Despite the fact that in 2022 the concept of «recloser» will celebrate its 30th anniversary, in our modern (everyday) life, it entered relatively recently, as well as the devices themselves. Why did it finally happen? What is hidden behind this exotic name? How, what, how much… All these questions we asked a specialist in this field, the development director of the electrotechnical company «E.NEXT-Ukraine» — Serhii Kucherenko.

Serhii KUCHERENKO is 40 years old, graduated from Zaporizhzhia National University with a degree in Foreign Economic Relations Management. He has been working in the electrotechnical market for 10 years. In E.NEXT company for 4.5 years. His hobbies are electronics, smart home, electric cars.

• Serhii, in November 2019 at the exhibition «POWER ENGINEERING FOR INDUSTRY» you made a report on «The use of E.NEXT reclosers within the Smart Grid concept». At the time, it seemed like a distant future, but now it's here. There are a lot of questions. What happened is one of them, but let's start from the beginning. What is a recloser, what is its purpose, what is the principle of operation, where is it used?

Reclosers are used mainly on overhead power transmission lines with a voltage of 6-35 kV. The recloser is a breaker that protects the transmission line from short-circuit currents and other damage. Another definition of a recloser is a sectional point intended to divide the network into sections and automatically separate the damaged area from the network. For example, a recloser can be installed on transmission lines that connect several settlements. If the line is damaged in one locality, the recloser will turn it off, but other settlements will remain energized. If the recloser is not installed, all settlements on this line will be left without electricity.



• What is the design of the recloser? Its main elements and functionality?

Typically, the recloser includes a three-phase vacuum breaker with built-in current and voltage sensors, a control cabinet, potential transformers, the control cabinet for power, and mounting on the pole of the transmission line. Regarding the functional purpose. Distribution system operators (DSO is name for oblenergos) have SAIDI and SAIFI indicators. SAIDI (System Average Interruption Duration Index) — an index of the average duration of interruption of the system or the amount of time that consumers were disconnected from the network when there was no power supply. And the SAIFI (System Average Interruption Frequency Index) is the index of the average frequency of outages, how many times this has happened over time. These indicators are very important for all DSO. So reclosers help to improve the duration and frequency indicators of outages.

As I said, the recloser is installed for partitioning the network. And in the event of damage to the line behind the recloser (for example, a short circuit), the recloser will turn off only the number of consumers who are after it. Consumers who are in it will be left with electricity. Тhereby it reduces the frequency of outages. In addition, you can use the recloser to reduce the duration of outages. One of the main functions of the recloser is manual or automatic reclosing (MR and AR). Manual — this is when the operator can remotely turn on the recloser. In automatic mode, the recloser itself tries to turn on the line. The fact is that the damage to the line is mostly unstable and self-healing. For example, due to strong winds, the phase wires may touch each other for a short time. In such cases, the recloser tries to restore the power supply itself using the AR function. By the way, self-repair of damage occurs in 50-90% of cases. If the damage persists, the recloser will turn off again after the AR cycle, if the damage is self-healing, the power supply will be restored and the duration of the shutdown will be reduced. As a result, SAIDI and SAIFI are improving.





• That is, reclosers have replaced some other devices that performed similar functions, or are they fundamentally new devices?

No, reclosers have not replaced such devices, just very few have been installed before. The peak of installation came in 2020-2021, and before that they were installed relatively rarely in Ukraine.



• And why didn't they do it before: because this is expensive equipment or it didn't exist in Ukraine at all?

Yes, reclosers are quite expensive, but the concept of RAB tariffs (Regulatory Asset Base), which came into force in 2021, has made it financially possible to invest in such equipment. RAB tariffs encourage DSO to modernize networks, improve the quality of services, in particular, to reduce the frequency and duration of outages, for which SAIDI and SAIFI indicators are responsible. And reclosers are currently the best option in the world to improve these indicators. We are now about 10 times behind the European SAIDI and SAIFI indicators.



• And what is the order of prices, how much is one recloser?

Often oblenergo orders a recloser with an installation service. Such a recloser with services can cost about half a million hryvnias. The share of the recloser itself can be a little more than half of this value.



• What is the payback of the recloser?

If the recloser is installed in the right place, according to our calculations, it is three to four years.



• And how many reclosers to install effectively on the line?

It depends on the line itself. For example, there is a line between two substations, with two-way power supply, 10 kW. It is effective to install two or three reclosers on this line. But if there is one substation, and it comes out of the line, radial, it is effective to install 1-2 reclosers. The payback of each subsequent recloser will increase greatly. Therefore, there are such approximate standards.

By the way, branches can go from the line. And if these branches are problematic, for example, go through the woods, it makes sense to install reclosers on such branches. The DSO has statistics on problem areas, and reclosers can also be installed on them if necessary to manage the entire system more efficiently.

Damage indicators are often used with reclosers, particularly in European countries. They allow you to keep track of where a problem has occurred on the line. The emergency team, moving along the line, can see where the LEDs of the indicator are flashing, where the damage occurred. The recloser together with the sensor speeds up the time of finding and eliminating damage. Consumers get electricity faster again.



• Going back to your recloser, how accessible is it compared to competitors?

Yes, cost is an important parameter. Before we entered the Ukrainian recloser market, the recloser cost was half as high. With our coming to the market, the competition has increased. And competitors were forced to lower the price for DSO, which allowed DSO to buy more reclosers.

Each operator has its own investment program for each year, there are funds. If there are savings, you can buy additional equipment. I believe that entering the market of reclosers «E.NEXT Ukraine» is a positive moment for all of us, because we all pay for electricity, and the tariff we pay also consists of DSO investments for the purchase of equipment.



• Is there a lot of competition in the market?

Competition exists. The main competitors were and remain «Tavrida Electric» and NOJA Power.



• And when did you enter the market?

At the end of the 2019, beginning of the 2020, we started to work with our new recloser.



• And who are your customers?

Poltavaoblenergo, Zaporizhzhyaoblenergo, Khmelnitskoblenergo, DTEK Networks — Dnipro Regional Networks, Kyiv Regional Networks, Kyiv Electric Networks, Odessa Regional Networks, Donetsk Regional Networks, and others. In total, about 10 DSOs.



• What are the requirements for reclosers?

There are international standards. For example, the standard IEC 62271-111. It defines the basic parameters of reclosers. Manufacturers who are certified according to this standard have certain advantages over others. So our recloser E.NEXT has a European certificate from the world-renowned Dutch laboratory KEMA.

Due to the presence of an international certificate, we were accredited in accordance with DTEK's technical requirements. As for other characteristics, for example, if you take our recloser, it has some differences from those that are currently on the Ukrainian market. These are both design and intellectual differences, software…



• You say — our recloser, our development. Is it a development of E.NEXT or is it a development of another company whose equipment is supplied by E.NEXT?

We took the Rockwill recloser as a basis and worked with their engineers to meet our needs. In Ukraine, all electrical appliances must comply with the REI (Regulations for Electrical Installation). We have developed a recloser according to these REI, it is KEMA certified and we use it as a breaker. We also use a controller for this recloser. Some of its properties are similar to those of competitors, and some are superior to ones.

So the recloser is our development, we install them under the E.NEXT trademark. This year we have installed more than 300 reclosers. Compared to the Ukrainian market, where about 500 reclosers have been installed in a year, this year we have become the market leaders in Ukraine.



• How did you become a leader?

We have gathered a team of specialists who have developed solutions based on the requirements of domestic DSO and taking into account these requirements, we have offered the market a perfect product: both in terms of characteristics and price. We managed to become leaders in just two years, and this is an achievement we can be proud of.



• How fast can you install reclosers? Are they available, do they need to be made, somehow prepared for specific requirements?

Now we have reclosers in stock. We will need one or two days to prepare them for the specific needs of the DSO. What does it mean to prepare? It means on what pole it wil be installed. It is important to know how many potential transformers will be used — one or two. What matters is the type of connection. It is necessary to know this to configure the recloser to communicate with the SCADA control system.

The recloser is installed at least per day (if one pole and one recloser). But more often several reclosers are installed at once, so in first day the poles are installed, and every next day — for one recloser.

Therefore, in ideal circumstances, it takes about three days from the time of order to the coming information from the recloser to the operator in SCADA. There is another option when ordering many reclosers. Then we make an order for the plant that produces, and within a month or two reclosers come to our warehouse, and there — according to the first scheme.



• Do you provide a warranty on your products?

Our reclosers are guaranteed for five years, and we are obliged to ensure their maintenance and operation for five years.



• As for the perfect product, what is your best recloser?

For example, for complex line protections, such as non-permanent arc earth faults and the determination of the second harmonic magnetizing current of the transformer. This makes it possible to distinguish a short circuit from a magnetizing current and to block the recloser from turning off when starting the transformers. If this is the start of the transformer, it is undesirable to turn off the line. And our recloser will determine this by the second harmonic and will not open the line when it is undesirable. Our competitors do not have such a function at the moment, this is our advantage!

Also, non-permanent non-metallic arc earth faults cause an increase in voltage, which often leads to a two-phase earth fault, as well as a more dangerous interphase short circuit. To determine such damage requires a controller whose performance is several times better than competitors. We have a sampling frequency of the controller of 6400 Hz, and in most — 1600 Hz.

Another advantage of our recloser is the spring drive. This affects the transient resistance: the lower the better. The lower the power loss, the more reliable the recloser. For example, breakers at 35/110 kV substations always use a more reliable spring drive.

There is also a magnetic drive that we do not use. There is less clamping force of the main contacts and greater transient resistance. This is a greater loss of electricity, this is a greater risk of welding contacts. Another advantage of the mechanical drive is that it can be turned off or turn on mechanically.

This is done using a dielectric rod from the ground. Competitors who use a magnetic drive do not have the ability to turn on the recloser with a bar.

Also, our recloser poles are located outside the body. The body is made of 4 mm thick stainless steel, the poles are on the body and they are separated by air.

They are serviceable. If the pole fails, it can be replaced. And there is no risk of an internal explosion. In some competitors, the poles are located inside the body.

Accuracy of operation is important for the recloser. This is due to the time-current characteristics of the devices, the dependence of operation on time and current.

And there is an option when the curve of time dependence on current is used. For example, if the current is 100 A, the shutdown will occur in 20 milliseconds, and if 200 A — instantly. These dependency curves are typical for both microprocessor relays and mechanical relays, such as RTV1 and PT80 Soviet type. They all have their curves. So in our recloser we with the developer of the microprocessor control device added curves that mimic the curves of mechanical relays that are still used on the lines. And we can adjust from them more precisely that there were no false positives. Thus, we are adapting to the realities of Ukraine to meet the needs of the DSO.

In addition, our control cabinet is thermally insulated, even though most DSOs do not. It has heating and forced ventilation.

There is protection against pulse overvoltages. We have developed a convenient design of the grounding of the cabinet, which saves time when installing the recloser.

Our recloser can work autonomously in the absence of energy for three days.

Our controller also has a function to monitor the quality of electricity. It can control the coefficient of nonlinear distortion, current and voltage imbalance, interruptions in the supply of sagging and voltage spikes. If you enable and monitor this feature for a month, you can detect and prevent problems on this line in advance.

Our recloser has a function to determine the location of damage in kilometers with an accuracy of around one hundred meters. To do this, enter all the line parameters in the recloser (resistance, length, etc.). Relevant information is received by the operator, thus reducing the amount of time to search for damage.



• So the recloser does this even without setting the damage indicators?

Yes, but the indicator still helps. For example, there is a trunk line, and there are branches. The recloser may indicate that the damage is 10 kilometers away. And it can be either on the line or on the branch. And the damage indicator will accurately indicate the direction.

Due to the fact that the processor in our recloser is quite powerful, we can determine the type of damage on the oscillogram, the reason for which the shutdown occurred. The oscillogram shows how the current and voltage, the reactive component, how the shutdown signal was applied to the recloser, how long it turned off, and whether these parameters correspond to the settings. The more powerful the processor, the more accurate the data, the better the result.

Our recloser can record waveforms, a maximum of 128 measurements per cycle. The cycle is 20 milliseconds. Due to this frequency of measurements, you can track the harmonic component, and see what is not visible with less discrete measurements. For example, most have 32 measurements per period, and we have 128 ones. Do you feel the difference?

And we have a processor that has a data transfer function according to the IEC 60870-5-104 protocol, there is also a modification of the processor that transmits data according to the IES 61850 protocol. The so-called digital substation protocol. It helps to standardize the principles of the substation, regardless of what equipment will be used there. This is a very progressive protocol used in Ukraine. We are setting up such a system in DTEK's Odessa regional networks and plan to develop this experience next year.

By the way, this year we have a good precedent when we installed the recloser not on the overhead line, but on the substation. What is the advantage? For example, 35 kV oil circuit breakers are planned to be replaced at the substation. It takes a lot of time. There are no current and voltage sensors on the breakers, and they are already built into the recloser. This helps reduce setup time, connection time of these breakers. The recloser is a complete device, and it speeds up work. And given that the difference in cost is not significant, it makes sense to use the recloser. Therefore, we plan to expand this experience of installing reclosers at substations. It is used in the world, it is not our invention, because it is really convenient.



• Can we say that this is a certain diversification of the recloser market?

Yes, this could be a diversification of the market, and it could be a surge if the DSO realizes that it is advantageous to install reclosers at substations.



• How do you estimate the recloser market now and in the future? Will it develop just as intensively?

In 2020, the recloser market in Ukraine was somewhere up to 300 units. Then we set about 100 units. In 2021 there was a peak (a total of about 500, we installed almost 300). This year's leap was caused by the significant need of regional power companies for reclosers. It was like a vacuum that needed to be filled, and it happened.… All DSOs are obliged to plan and develop investment programs for the next year. Analyzing these programs, we see that in 2022 it is likely that less will be installed, up to 400 units on airlines. At the same time, we hope that the number of installed reclosers at substations will increase.

Everything will be E.NEXT 😉

The interview was published in the magazine "Ukraine Electro" №6, 2022

https://ua-electro.com/reklouzer-yak-instrument-energoefektivnosti-merezh/