Basics of checking the ground loop in video devices
A ground loop is any circuit in which more than one ground source extends between electrical devices. Lack of grounding in CCTV equipment can cause numerous problems, including wavy lines and poor video quality.
A camera connected to a grounded wall transformer 100m from the recorder will most likely be grounded to a different circuit breaker than the recorder. This allows you to identify and know that there may be a difference of several volts between 2 power supplies.
To check the ground loop
- Set the voltmeter to its most sensitive setting.
- Disable the camera you want to test.
- Place one pin on the case (try using a screw on the case to provide a ground connection).
- Place the other pin on the outside of the connector.
Any value higher than zero, as in an apartment, indicates a missing ground loop. Any value above 0.1V is out of tolerance for proper recording.
Basic rules for checking grounding
To ensure safe and reliable operation, use a multimeter or tester to check the AC outlets in your home. Before connecting to an AC power source, perform tests on the AC power source.
Namely:
- Turn off the circuit breaker that powers the panel. Attach tag S229-0237 to the switch.
- Use a ground resistance meter to check the resistance between the receiver's ground pin to each of the phase pins. The test checks for short circuits to ground or wiring.
- Use a ground tester to check for infinite resistance between phase pins. The test checks short wiring.
- Use a multimeter to measure the corresponding voltages between phases. Use a multimeter to check that the voltage at the AC outlet is correct.
How to protect yourself from zero loss
How to deal with this? There are several ways to protect yourself from increased voltage when the zero line breaks.
The first method is to reliably re-ground the neutral conductor. Looking ahead, I’ll say that this method is bad and harmful.
This method can be used in private homes
It doesn’t matter if you have single-phase or three-phase input. The most important thing is to make a high-quality grounding circuit
After this, connect the neutral conductor busbar to this circuit with a separate conductor. In the event of a break in the neutral wire, the power supply to your household appliances will remain in balance and no major imbalance will occur.
The current will flow from the phase through the consumer resistance and go through the zero busbar and its conductor to the ground. And so on for all other phases.
A slight imbalance will of course be present here, but its magnitude will depend on the quality of your ground loop. However, this method of protection has one big drawback that negates all its advantages.
Of course, a grounding loop needs to be made, no one argues with that. The question is whether to connect it to the neutral conductor.
After all, if it is of high quality (10 Ohms or even 4 Ohms) only you have along the entire street, and a break in the neutral wire happens not near your house, but at the very beginning of the overhead line, then all your neighbors will immediately “sit” on this circuit.
In fact, the entire total current will go through your neutral conductor. If you set zero through a two-pole or four-pole circuit breaker, it will most likely break due to overload. Otherwise, expect a fire and melted wiring.
Therefore, a correctly assembled shield (an input circuit breaker selected for the load, grounding a copper conductor with a cross-section of at least 10 mm2) is the key to your safety.
Another disadvantage of such “circuit protection” is the danger of getting energized yourself. Let's say you made a great outline a few years ago.
But due to the presence of salts in the soil, it gradually rotted, and you don’t even know about it.
As a result, with the next neutral break, all grounded electrical equipment in your home will be energized. There is no land anymore. And the phase potential will begin to flow through the instrument housings.
I went to open the refrigerator and got an electric shock; I went into the shower and got electrified.
Therefore, it is more reliable and safe to use another method.
Electrical installation Ivanovo - Zeroing: will it protect or kill?
Hello, friends!
In this article we will talk about what zeroing is, where it is used, as well as the main errors in its design. The topic is not easy, and there are constant debates on forums.
It is interesting that often even electricians cannot correctly say how grounding differs from grounding. Let's figure it out. First, let's see what the PUE says about zeroing.
Simply put, grounding is the connection of the body of an electrical device with the neutral wire.
Now let's see what the PUE tells us about grounding
note
Grounding of any part of an electrical installation or other installation is the intentional electrical connection of this part to a grounding device.
In simple words, grounding is the connection of the body of an electrical device with a ground electrode. A ground electrode is a structure made of metal pins driven into the ground.
Now let's look at how the most common power supply systems for apartment buildings work.
Old, Soviet TN-C system
More modern TN-CS system
Both schemes use a combined neutral conductor PEN, which is grounded at the transformer substation.
If you look closely at the diagrams, it becomes clear that the working zero is always connected to ground, that is, grounded. And the question arises: what, exactly, is the difference between grounding and grounding? After all, by connecting the body of the device to the working zero, we actually connect it to the ground.
In fact, there is a difference. It lies in the principle of action.
Grounding is designed to drain current to ground. This reduces the dangerous voltage on the body of the device or device.
Grounding is intended to create a short circuit effect during phase breakdown on the housing. At the same time, the machine is activated and turns off the emergency line.
Important
Thus, grounding and grounding in TN systems work simultaneously, so to speak, in one bottle. Therefore, the 3rd protective contact in Euro sockets in TN systems is both grounding and neutralizing.
Based on this, it is correct to talk about a combined conductor PEN, a working neutral conductor N and a protective conductor PE. At the same time, even electricians do not always understand the difference between PE and N, but it is very significant.
Usually, when some “electrician Uncle Vasya” talks about grounding, he means various kinds of collective farms such as jumpers in sockets and the like connecting the protective wire to the neutral wire. And it's dangerous.
Incorrect zeroing can, instead of protection, cause a tragedy. And such pseudo-protection occurs very, very often.
Let's figure out how protective grounding is done correctly and what absolutely should not be done.
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Remember, the division of the combined conductor into a working zero and a protective zero must be done in a common house input device (IDU). And from there the protective conductor must go to the floor panels, and from them to each apartment.
Thus, we get a five-wire riser: 3 phases, working zero and protective zero. In this case, we are not talking about the so-called grounding, since each apartment receives a separate protective wire (TN-CS and TN-S systems). It needs to be connected to the third contact of the sockets.
In old houses with non-modernized wiring, there is usually a four-wire riser: 3 phases and a combined neutral PEN (TN-C system). This is where the complete chaos and terrible mistakes begin.
Advice
It all starts in the floor panel. Often it makes an independent division of PEN into PE and N.
Rule 1. In single-phase circuits, it is prohibited to separate the neutral wire (PUE - 1.7.132).
How to determine which network is in your home? In relatively old houses, the access risers are four-wire: three phases and one combined neutral (PEN). That is, three-phase risers are used, respectively a three-phase circuit.
In very old houses, Stalin and Khrushchev buildings, a two-wire riser is often used, in which there is only a phase and a working zero. A distinctive feature of such houses is the absence of access panels. The risers go in the shafts between the apartments, and in the apartments themselves there are specific “humpbacked” shields. In such houses, as a rule, a single-phase network is used.
Rule 2. The combined PEN conductor must have a cross-section of at least 16 mm for aluminum or 10 mm for copper.
Rule 3: Once PEN is split into PE and N, they cannot be reconnected.
Here, I think, no explanation is needed.
Rule 4. The protective conductor PE must not be disconnected.
That is, you cannot install machine guns and other disconnecting devices on it.
Rule 5. PEN must be separated BEFORE all machines, switches, switches.
It’s better to do this: take a brass busbar and screw it to the shield so that there is contact between them. Make a branch from the zero riser through a separate nut to this bus. Connect the PE protective wires from the apartments to the bus.
If at least one of these rules is not followed, then it will not be protection, but a life-threatening collective farm.
A little more about what not to do
1) Connect the protective and neutral contacts in the socket with a jumper. This is one of the most dangerous mistakes!
note
If the zero burns out, is damaged, or is accidentally disconnected, dangerous phase voltage will immediately appear on the housing of all devices connected to such sockets. In this case, neither the RCD nor the machine will work. Hello death.
The same effect will occur with a random change of phase and zero.
2) Place the neutral and protective conductors on one screw in the shield
PE and N must be on different terminals (busbars). Moreover, each wire from a separate apartment must be clamped with a separate screw.
3) Zero to an ungrounded (non-zeroed) shield.
Typically, all panels have direct contact with the zero or protective riser (zeroed). But sometimes there is no contact, for various reasons. For example, the connecting wire fell off. Grounding such a shield can lead to the appearance of dangerous voltage on its body.
In practice, this kind of jambs are found all the time, in various variants and combinations. I can advise you not to be lazy, study the PUE, and also not trust your wiring to dubious individuals.
Protection with voltage relay
This method is suitable for both private houses and apartments in high-rise buildings. All that is needed to protect against voltage surges and 380V in sockets is to install a modular voltage relay inside the input panel.
At the same time, it will protect appliances and the refrigerator from both increased and decreased values. There are models that are additionally equipped with built-in overcurrent protection.
The article below will help you learn more about their varieties and choose the right model for you.
If your panel is already fully equipped, and it is impossible to place additional modular devices there, then use small voltage relays that simply plug into an outlet.
Although the functionality of modular and socket options may differ, they perform their main task - protecting electrical appliances - equally well.
Today, voltage relays are the most economical and effective way to deal with voltage surges. Stabilizers may not be suitable for everyone.
Moreover, some devices will not even save you from an instant jump. One way or another, causing a fire and failure of expensive equipment.
Therefore, always install voltage relays in your houses and apartments. These devices cost an average of 3,000 rubles and will help you save hundreds of thousands in the future.
How to distinguish between working zero and protective grounding
Of course, you should not check the resistance between the “neutral” and “ground” wires, especially if the power system is energized. No one will let you into the common control room either. Therefore, we will check the correctness of the separation of zero and ground using a multimeter (household tester).
Since the input points of grounding devices (zero at the substation and the grounding bus in the house) are located at a distance from each other, there is a certain resistance between them. The soil, even wet, is not an ideal conductor. If we organize an electrical circuit without a load, we will see the difference in potentials.
We connect the measuring device to the phase contact and the working zero. In the diagram this will be circuit “A”. We fix the value.
We immediately connect the tester to the phase wire and the protective zero contact. In the diagram this is circuit “B”. There is no difference in potential: the device will record the same voltage value. Why did it happen? When the working and protective zeros are combined, the current in both measurement options actually flows through the same wire. The resistance does not change, there are no losses, and there is no voltage drop.
If your measurement results show the same voltage, the wiring is connected in violation of the Electrical Installation Rules.
What happens when the working field and protective grounding are separated?
When the device is connected to phase and zero, there is practically no voltage drop (in the diagram this is circuit “A”). You will see the actual value of the operating voltage in the network. By connecting the tester to the phase wire and protective ground, you measure the potential in a long circuit. To complete the circle, an electric current (circuit “B” in the diagram) passes through the real ground between the physical contact points of the “ground”. Considering the soil resistance, a voltage drop of 5% to 10% will occur. The device will show a lower voltage.
This indicates that your electrical wiring is organized correctly, you have a true distributed protective ground. With properly selected machines, electrical equipment and users are reliably protected.
We figured out what the difference is between grounding and neutralizing. The benefits of proper organization of power supply are obvious.
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It is clear that when carrying out major repairs, electricians will replace the wiring in accordance with the Electrical Installation Rules. At a minimum, three independent wires will appear in your input panel: phase, working zero and protective ground. All that remains is to replace the wiring in the outlet network.
But major repairs can be carried out in a few years, and today you are already using a boiler and washing machine without grounding, or even worse - with a protective grounding. There is only one way out: organize grounding yourself. If you live in a private house, the technical side of the issue is significantly simplified. But for high-rise buildings, the cost and complexity of the work depends on the floor.
An alternative is to organize a grounding bus with your neighbors, with junction boxes on each staircase.
The tire must be one-piece until it is inserted into the ground. Near the foundation, preferably not in the road surface, but in a flower bed, a grounding loop is organized in accordance with the Electrical Installation Rules. Each resident of the entrance can connect to the common bus and bring “ground” into the apartment. Then there are two options:
- Organize a grounding contact group in the distribution panel, and replace all electrical wiring with three-wire wiring.
- Inside the baseboard, stretch the earth cable under each socket and insert it into the mounting boxes.
Either way, you will protect both your electrical appliances and, most importantly, your health.
The fact that “land” cannot be taken from the working field is clear from our material. There are people who like to ground themselves on water supply or heating pipes. Theoretically, the steel pipe has a connection with the ground. In practice, there may be inserts made of polypropylene pipes along the riser, and there is no contact with the “real ground”.
In addition to the fact that you do not receive reliable grounding, your neighbors are at risk, who can receive an electric shock simply by holding the radiator.
Home » Grounding » Is it possible to connect grounding to zero
Generally speaking, it can be noted that the great and terrible power of electricity has long been described, calculated, and entered into thick tables.
The regulatory framework defining the paths of sinusoidal electrical signals with a frequency of 50 Hz can plunge any neophyte into horror with its volume.
And, despite this, any regular on technical forums has long known that there is no more scandalous issue than grounding.
The mass of conflicting opinions does little to establish the truth. Moreover, this issue is actually serious and requires closer consideration.
If we omit the introduction of the “electrician’s bible” (PUE), then to understand grounding technology you need to turn (to begin with) to Chapter 1.7, which is called “Grounding and protective measures for electrical safety.”
Electrical installations with regard to electrical safety measures are divided into:
- electrical installations above 1 kV in networks with an effectively grounded neutral (with large ground fault currents), ;
- electrical installations above 1 kV in networks with an isolated neutral (with low ground fault currents);
- electrical installations up to 1 kV with a solidly grounded neutral;
- electrical installations up to 1 kV with insulated neutral.
A solidly grounded neutral is the neutral of a transformer or generator, connected to a grounding device directly or through low resistance (for example, through current transformers).
The term is not entirely clear at first glance - neutral and grounding devices are not found at every turn in the popular science press. Therefore, below all unclear places will be gradually explained.
Advice
Let's introduce a few terms - this way we can at least speak the same language. Perhaps the points will seem “taken out of context.”
But the PUE is not fiction, and such separate use should be completely justified - like the use of individual articles of the Criminal Code.
However, the original PUE is quite accessible both in bookstores and online - you can always turn to the original source.
- 1.7.6. Grounding of any part of an electrical installation or other installation is the intentional electrical connection of this part to a grounding device.
- 1.7.7. Protective grounding is the grounding of parts of an electrical installation in order to ensure electrical safety.
- 1.7.8. Working grounding is the grounding of any point of live parts of an electrical installation, which is necessary to ensure the operation of the electrical installation.
- 1.7.9. Grounding in electrical installations with voltages up to 1 kV is the intentional connection of parts of an electrical installation that are not normally energized with a solidly grounded neutral of a generator or transformer in three-phase current networks, with a solidly grounded output of a single-phase current source, with a solidly grounded midpoint of the source in DC networks.
- 1.7.12. A grounding electrode is a conductor (electrode) or a set of metallic interconnected conductors (electrodes) that are in contact with the ground.
Correct voltage between neutral and ground
Zero is the return path for the alternating current circuit, which must withstand it in normal condition and properly maintain the proper operation of electrical appliances. This current can be caused by many reasons, mainly due to phase current imbalance. There may be other reasons, but the magnitude of this current is in analogy with the phase current, and in a few cases it can be twice the phase current. Thus, the neutral wire is always considered charged (in an active circuit). This neutral wire is fed to ground (ground) so that the second terminal of the neutral wire is zero.
While the phase and neutral are connected to the main power wiring, the ground may be connected to the frame of the equipment or to any system which does not normally carry current, but in the event of some insulation failure, must carry some minor charge. The voltage between zero and ground is also called common. The sources for common mode voltages on power lines vary. They can occur at higher power line frequencies (with switching mode power supplies and non-linear electronic loads of modern equipment).
Peculiarities:
- A frequency of 50/60 Hz is simple, but it is possible to drop to 45 Hz in the neutral conductor. It increases in balance in 3-phase loads since the neutral is usually reduced.
- After all, for 3 phases 1 neutral is usually used, and ideally this current is 0 (for balanced loads).
- The phase currents cancel each other out, but with balancing comes more current, which causes them to drop, especially when this neutral is reduced.
If other sources are connected at high frequency, then the common mode voltages are mismatched due to electronic switching and induced noise from external sources.
Why is this happening?
Typically, an unpleasant tingling sensation occurs when a person touches some grounded metal surfaces, such as a battery radiator under a table, and at the same time holds his hands on a metal part of the computer.
In my case it was the grounded metal edge of the tabletop. If you touched the edge of the tabletop and the MacBook at the same time, a noticeable tingling sensation appeared in your hands. And this is a completely normal situation. The fact is that in the circuit of the computer power supply there is a noise filter, the filter input is made on two capacitors connected on one side to each of the wires of the 220-volt network, and on the other their common point is connected to the case. The result is a 220 volt voltage divider in half. This is where 110 volts appear on the body.
Simplified circuit of a computer power supply noise filter
The picture above shows a simplified circuit of the noise filter in the power supply. As you can see, both capacitors are connected to the protective ground (yellow wire E), which in turn is connected to the device body. If the power supply is connected to a socket without grounding, then half the voltage of the mains voltage appears on the case. In this case, the current flows in this circuit is small, but it is quite enough to cause discomfort or a slight spark if it is touched by another device with proper grounding. This is how you can observe small sparks when trying to connect two devices with a cable in cases where one of them is connected to a grounded outlet and the other without.
