Networks up to and above 1000 volts. What are the differences?

Briefly and clearly! Thanks!

Well, of course, it’s clear and understandable, but in networks with isolated neutral, a single-phase earth fault is not short. If we are dealing with short circuits, then their protection will be disconnected necessarily, unless of course they work properly.

Further, voltage classes above 1000 V have a gap between the neutral of the receiver and the ground, this is so, but only in a certain range of voltage classes. If we take 110 kV, then this is usually a network with an effectively grounded neutral, that is, the connection of the supply winding of the receiver has a connection to the ground.

Nikolay, yes, according to formal features, a ground fault in networks with isolated neutral is not short. But such is often referred to by habit.

About networks with voltage of 110 kV and higher, perhaps, it was necessary to mention an effectively grounded neutral. (not directly to the ground, but through the reactor).

And tell me please, does the TV (old tube) apply to the electrical installation "above 1000 V"? The voltage on the horizontal transformer reaches several tens of kV.

What are the criteria for qualifying an electrical installation? Or is the supply voltage of the electrical installation itself the main criterion, but everything that is obtained inside it is not that important?

Igor: TV is not an electrical installation at all, but a device. An electrical installation is a combination of devices, apparatuses, lines and structures that contains them.

In other words, your apartment, in which the TV stands, is an electrical installation up to 1000 V, and the TV is a device in its composition.

The whole question is that in the documents "Secondary Radar Maintenance Instructions ..." some wise guy wrote that this setting refers to the settings "Above 1000 V". Although the supply voltage is 380V!

In addition, the frequency in this setup is not 50 Hz, but 400!

Justification is required of me. Why am I not equipping this electrical installation with protective equipment as an electrical installation "Above 1000 V"

Well, qualification groups of personnel should be appropriate ...

We even demonstrated how to set up this equipment without shutting down, using a conventional screwdriver and even with an uninsulated sting ... And we showed the arcing ...

It must be correctly stated on paper. Here's how to do it. You need at least a couple of “smart” phrases.

And according to formal features, is this radar an electrical installation, not a device? Then, probably, you can’t argue.

All the complexity is due to the fact that there is a line in the instructions.

And what happens? Now, having attributed the locator to the High-voltage installation, it is necessary to equip it with gloves, bots, rods ... and work in a helmet and a protective shield ... Bullshit.

So I say that the only way you can avoid this is to run into the definition of "electrical installation" and prove that the locator is not it, that it is a device. Like a tv. And in his regard, it is impossible to apply requirements to installations over 1000 volts.

Igor, Igor, as I understand it, there are no live parts in the radar above 1000 V. Therefore, this device is not an electrical installation above 1000 V. I think that it is necessary to amend the radar maintenance instructions. Contact the service that approved this manual with the appropriate request. Show them the diagram of this device so that it can be clearly seen that the radar does not have live parts with an operating voltage above 1 kV.

If you are required to have appropriate protective equipment, then why did they allow the demonstration of equipment settings without shutting down and without taking appropriate safety measures? Direct violation of EECP.

Well, if there is still a high voltage in this device, then they are absolutely right and it is an electrical installation above 1 kV. Accordingly, to ensure the safety of maintenance personnel, it is necessary to apply electrical protective equipment and apply appropriate safety measures.

Do you say the arc was demonstrated? Was there a long arc?

I did not read the comments, but I would like to correct the author. (Perhaps already corrected). Networks over 1000V are divided into several categories: 1- with a solidly grounded neutral, 2- with an effectively grounded neutral 3- grounding with high resistance, and with an isolated neutral. As a rule, 6-10.35 kV networks are with isolated neutral, or with high resistance. 110kV - effectively grounded neutral. 220kV network with a dull earthed neutral.
Then about this -But the fact that the leakage current to the earth is small does not mean that it is safe. Just the opposite. Such a current is more insidious: protection devices may not detect it at all, and if they do, they will only signal but not turn off.
There are already a lot of microprocessor protections that can detect and disable a damaged area. It all depends on what the protection will be configured - shutdown or signal.

Serge, and why only microprocessor? Protections of the old model, which are built on electromechanical relays, are also sensitive and able to detect ground faults. At a voltage of 6 (10) kV, earth fault protection responds to the presence of earth leakage current. In 35 kV networks, these currents are very small, so the relays record the value of the fault voltage not ground. Microprocessor protection, of course, is more accurate, but the old ones are also not inferior to anything - they fix even minimal distortions.

Earth fault protection in 6-35kV networks always works on signal. If they worked on shutdown, then consumers would often be de-energized. For example, the 35kV line feeds an entire area: a couple of villages, villages, small enterprises. In this case, it is most advisable to identify the damaged area and disconnect it from the network. However, most consumers will remain in work. If the protection acted on shutdown, then every time, even if there would be a false operation of the protection (blown VT fuses, unbalanced load, phase failure of the power transformer, etc.), consumers would be de-energized.

MaksimovM,
Yes you are right, old-style protections can do this too, built on relays RTZ, ZZN, ZZP, etc.
Just microprocessor - much more opportunities. Yes, and there was no time yesterday to write about it, that it occurred to me and wrote))))

SergeI agree about the versatility of microprocessor protections, but they also have disadvantages. They are more demanding on the temperature in the room, often software crashes.

With regard to accuracy, he personally witnessed that the microprocessor relay protection device Ref 630, installed on the 10 kV side of the substation power transformer, did not detect voltage distortion, which was a result of a fuse blown on the high side of the 10 kV section voltage transformer. According to the testimony of a kilovoltmeter for monitoring the insulation of this section of tires, there was a noticeable distortion of linear voltages. At the same time, there were no corresponding signals on the terminal of this section. In this case, the substation personnel learned that the fuse had blown out by accident, checking the insulation control by kilovoltmeter.

At the same substation, there was a similar situation with the voltage transformer fuse of one of the 35kV sections. In this case, the terminal of this section showed the presence of land and the alarm worked. In this case, the personnel discovered the blown fuse on time and measures were taken to replace it.

But what about a 380v network with isolated neutral?

"... the neutral of the supply transformer of networks up to a thousand volts has an electric ground connection. This is done so that single-phase consumers of such a network, even with an asymmetric load, receive same power supply with phase voltage. "

A "ground connection" will not be able to "balance" the load.
All networks having overhead power lines, or having electrical contact with them are grounded, - cause: on metal objects (wires) isolated from the ground, a very significant charge can accumulate relative to the ground (electrostatics); if this charge is not neutralized, then it can destroy the electrical installation, cause fire and death; even if this network is "de-energized" and energy is not transmitted through it.

The difference between "high voltage" and "low voltage": different requirements for electrical insulation of tools, instruments and installations.
For example, the installation tool of the "low-march" has dielectric handles that impede the passage of current through the body of the installer; the “high voltage” mounting tool, on the contrary, has no insulation (bare metal).

As I understand it, the PUE (Clause 1.1.3) classifies Electrical Installations according to electrical safety conditions: up to 1 kV and above 1 kV. I can’t understand what a high or low voltage network is. High / low is what voltage (how much)?

The person who wrote this article clearly has no idea about the operating modes of the neutral of electric networks, and among other things, modern science has 4 (!) Four modes:
1) a deadly earthed neutral described in the article - This is when the neutral or zero point (if there is one, for example, if the windings of an electric motor or transformer are connected in a triangle, then the zero point is absent) of electric machines, transformers and other three-phase consumers “SOUND” (hence the name ) connects to the ground loop. As the author correctly noted, these are all networks up to 1000 V, as well as networks with a voltage of 330 kV and higher. And this is as much as the class 330 kV itself; 500kV; 750kV and 1150 kV. and here it is already not joining the written article.
2) the isolated neutral mode described in the article is when the zero point of electrical machines and apparatuses is isolated from the ground loop; these are networks, as a rule, with a voltage of 6 kV; 10 kV; 35 kV
3) resonant-grounded neutral is usually used only in 35 kV networks. this is when the neutral of electrical machines and apparatuses is connected to the grounding circuit through an arcing reactor, this is not always done and not everywhere to make a decision on the need to use this type of neutral grounding, it is necessary to do more than a dozen calculations of short-circuit currents to earth, both single-phase and double or two-phase to the ground
4) an effectively grounded neutral is when the neutral of the power transformers is grounded through a disconnector and can be grounded according to the instructions of the regime services; it is used in networks of 110 and 220 kV

So the statement of the author of the article that networks above 1000 V work with isolated neutral is true only for two of the nine voltage levels above 1000 V.

Alexander, electrical networks are divided into two classes - up to 1000 V and above 1000 V.An electrician serving electrical networks receives a tolerance of up to 1000 V or up to and above 1000 V, without limitation, up to 750 and 1150 kV. There is another concept - operational rights. After training and testing knowledge, an electrician can be given the right to service several distribution substations, power lines of various voltage classes. Moreover, one electrician can serve electrical installations with a voltage of, for example, no higher than 35 kV, and the other can serve electrical installations with a voltage of 330 kV or 750 kV. In both cases, electricians have a voltage tolerance of up to and above 1000 V, that is, without restrictions.

Regarding the operation modes of neutrals in electric networks, you also write untruthful information.

1) Electricity networks of voltage class up to 1000 V can have both a deadly grounded neutral and isolated. Grounding systems TN and TT provide neutral grounding. The IT grounding system has an isolated neutral.

3) Compensating reactors and arc suppression coils, on the contrary, are mainly used in 6-10 kV networks, since in these networks earth fault currents are ten times higher than in 35 kV networks.

Short-circuit currents in voltage networks of 35 kV are very small, therefore, even earth-fault protection does not record a change in currents, but voltages of zero sequence.

4) Effective neutral grounding is when not all transformer neutrals are grounded in 110 kV or 220 kV power networks. That is, a part of the transformers has a grounded neutral, the other part is not grounded, and it is necessary through a surge arrester or surge suppressor. Short-circuit currents are calculated, and based on their results, it is selected which neutrals of transformers should be grounded and which not - the main purpose of the calculations is to reduce short-circuit currents in all sections of the electric network. As a rule, the indication of the operating mode of the neutrals is constant. A change in the operating mode of one or another neutral transformer can only be in the case of changes in the configuration of electrical networks, the inclusion of new substations and, accordingly, transformers.

In both cases, not only disconnectors (ZONs), but also the so-called transformer “zero” short circuits, are used for neutral grounding. Regardless of whether the transformer neutral is grounded at the moment or not, between the ground and the transformer neutral to protect the neutral of the power transformer, an arrester or surge suppressor (arrester), designed for a voltage that does not exceed the nominal value for this neutral, is switched on.

Electrical networks with insulated neutral are used in electrical networks at a voltage of 380 - 660 V and 3 - 35 kV.

Good afternoon. Faced such a description of the KUGPP cable: Cables for control systems and alarm systems that do not spread combustion, are intended for the transmission of electrical signals and distribution of electrical energy in control circuits, alarm systems, communications, inter-instrument connections at voltages of 250, 380, and 1000 V AC with a frequency of up to 200 Hz or at voltage respectively 350, 750 And 1000V DC.
What kind of circuit is 1000V, I can’t understand.

Not on the basis of the type of grounding is divided up to 1000 and above 1000! This boundary is determined by the minimally safe distances to the fences of live parts. See "POT during operation of Electrical Installations" table 1. For example up to 1000V, the electric arc can be “stitched” when touching live parts (the minimum distance is not standardized - without touching the fences), for example. above 1000V and non-observance of min.distance to fences of live parts of the arc can "flash" through the air. Those. if you come closer than 0.6 m in the EU 1-35 kV to the fences, then there is a complete probability of electric shock.Higher voltage - more distance from fences.