Current program for calculating short circuit currents. Construction of a new network based on the equivalent. Calculation of electrical quantities at the location of damage

In this article, I want to introduce you to the "Emergency Emergency" program version 3.0.8. For those who don't know, this program is designed for calculating currents short circuit in networks up to 1000 V. There is a paid and free version. The paid version costs 15,000 rubles, in principle you can use the free version, if you use the free version, you will not be able to calculate short-circuit currents when supplying consumers with electricity from an autonomous generator and you cannot export the calculation results to separate file. As practice has shown, you can also use the free version. To get better acquainted with the "Emergency Emergency" program, let's look at an example of calculating TKZ.

Calculation example

Fundamental electrical diagram is shown in Fig. 1.

The power source can be a diesel power plant or a district network that supplies consumers through a step-down transformer. It is necessary to check the protection devices for disconnecting the short circuit at points K-1 and K-2 within the standard time.

For point K-1, the protection devices are circuit breaker, installed at the generator output in the diesel power station container, and fuses installed in the distribution panel of the transformer substation.

For point K-2, the protection device is a circuit breaker installed in the ASU-AVR panel on the MA1 line feeder.

All data necessary for the calculation is given on schematic diagram(see Fig. 1).

Point K-1 (G)

Calculation of the emergency short circuit mode and determination of the activation of the protection device at point K-1 when consumers are powered from diesel power plant(generator). All initial data and calculation results are presented in the program screenshots, see Fig. 2-6.

Point K-2 (G)

Calculation of the emergency short circuit mode and determination of the activation of the protection device at point K-2 when consumers are supplied from a diesel power plant (generator). All initial data and calculation results are presented in the program screenshots, see Fig. 7-10. Since entering the DES parameters is similar to calculating the K-1 (G) point, this screenshot is not shown here.

Point K-1 (T)

Calculation of the emergency short circuit mode and determination of the operation of the protection device at point K-1 when consumers are supplied from a centralized network (transformer). All initial data and calculation results are presented in the program screenshots, see Fig. 10-15.

Point K-2 (T)

Calculation of the emergency short circuit mode and determination of the operation of the protection device at point K-2 when consumers are supplied from a centralized network (transformer). All initial data and calculation results are presented in the program screenshots, see Fig. 16-19. Since entering the transformer parameters is similar to calculating the K-1 (T) point, this screenshot is not shown here.

Calculation results

According to the calculation results, the protection devices operate within the standard time when a short circuit occurs at points K-1 and K-2. At the same time, the operation of protection devices in emergency mode was tested when consumers were powered both from a diesel power plant and from a centralized network.

Designation of quantities

The report, database and calculation results of the program use symbols physical quantities. Below is full list their designations.

Transformer

• Uinn.nom., kV – Rated voltage high voltage windings;
• Unnn.nom, V – rated voltage of the low voltage winding;
• Snom, kV*A – rated apparent power;
• Unn, V – operating mode voltage of the LV winding;
• Ik.in., kA – short circuit current at the terminals of the HV winding;
• Sk, MV*A – short circuit power at the terminals of the HV winding;
• Xс, mOhm – equivalent inductive reactance of the system;
• R1, mOhm – active resistance direct sequence;
• R0, mOhm – zero-sequence active resistance;
• X1, mOhm – positive sequence inductive reactance;
• X0 – zero sequence inductive reactance.

Generator

• Snom., kV*A – rated apparent power;
• Unom., V – rated voltage;
• f, Hz – nominal frequency;
• U(0), V – generator voltage at the time preceding the short circuit;
• Рр, kW – estimated active load power of consumers;
• Qр, kvar – calculated reactive power of consumers’ load;
• Sp, kV*A – estimated total load power of consumers;
• Iр, А – calculated load current of consumers;
• cosф, p.u. - coefficient active power consumer loads;
• tgf, p.u. – reactive power factor of consumer load;
• f, deg. – the angle between the active and total power of the load of consumers;
• Xd”, p.u. – supertransient inductive reactance along the longitudinal axis;
• Xd’, p.u. – transient inductive reactance along the longitudinal axis;
• Xd, p.u. – synchronous inductive reactance along the longitudinal axis;
• Xq”, p.u. – supertransient inductive reactance along the transverse axis;
• Xq, p.u. – synchronous inductive reactance along the transverse axis;
• X2, p.u. – negative sequence inductive reactance;
• X0, p.u. – zero sequence inductive reactance;
• R, Ohm – active resistance of the armature winding;
• Td”, s – supertransient time constant along the longitudinal axis with the armature winding short-circuited;
• Td’, s – transition time constant along the longitudinal axis with the armature winding short-circuited;
• Ta, s – decay time constant of the aperiodic component of the armature current during a three-phase short circuit at the machine terminals;
• Ks or OKZ – short circuit ratio.

Line

• Npar., pcs. – number of parallel connected conductors;
• Fphase, sq.mm. – cross-section of the phase conductor;
• Fzero, sq.mm. – cross-section of the neutral conductor;
• t start, °C – initial temperature of the conductor;
• t pr., °C – design temperature of the conductor;
• R1 linear, mOhm/m – linear positive sequence active resistance;
• R0 linear, mOhm/m – linear zero-sequence active resistance;
• X1 linear, mOhm/m – direct sequence inductive reactance per unit;
• X0 linear, mOhm/m – linear zero-sequence inductive reactance;
• R1, mOhm/m – positive sequence active resistance of the line;
• R0, mOhm/m – active resistance of the line zero sequence;
• X1, mOhm/m – positive sequence inductive reactance of the line;
• X0, mOhm/m – inductive reactance of the zero sequence of the line;
• Dav. geom., m – geometric mean distance between phase wires (only for overhead lines).

Initial conductor temperature

• Inorm.calc., A – value of the line operating current in normal mode. In the case of several parallel connected conductors, the calculated current of the entire line is indicated, and not of an individual conductor;
• t ambient normal, °C – normalized temperature value environment. As a rule, when laying a line in the ground, the value is 15 °C, in the air - 25 °C;
• t ambient, °C – ambient temperature value;
• Iadditional cont., A – reference value for a long time permissible current(permissible continuous current) of the conductor. In the case of several parallel connected conductors, the current of an individual conductor is indicated, and not the entire line;
• t additional cont., °C – reference value permissible temperature continuous (normal) mode conductor.
• t start, °C – calculated value of the initial temperature of the conductor.

Other circuit elements

• Rpr, mOhm – total active resistance of other circuit elements;
• Xpr, mOhm – total inductive reactance of other circuit elements;
• Rk.s., mOhm – active resistance of contacts and contact connections;
• Rd, mOhm – active resistance of the electric arc;
• Rр, mOhm – active resistance of the reactor;
• Xр, mOhm – inductive reactance of the reactor;
• Rav, mOhm – active resistance of the circuit breaker coil;
• Xav, mOhm – inductive reactance of the circuit breaker coil;
• Rtt, mOhm – active resistance of current transformers;
• Xtt, mOhm – inductive reactance of current transformers.

Protection apparatus

• Inom, A – rated current;
• Irast., A – rated tripping current of the release (only for the circuit breaker) according to the passport;
• Tav.,s – response time;
• Кз – safety factor;
• Iav., A – operation current taking into account the safety factor.

Calculation results

• Ip(0), A – initial (time T=0 after the occurrence of a short circuit) effective value of the periodic component of the short-circuit current.
• Ip(Tav), A – effective value of the periodic component of the short-circuit current after a period of time Tav (see below) after the occurrence of the short-circuit;
• ia(0), A – the largest initial value of the aperiodic component of the short-circuit current.
• ia(Tav), A – the value of the aperiodic component of the short-circuit current after a period of time Tav after the occurrence of the fault.
• iу, A – shock current.
• Iter.ek., A – effective value of the thermally equivalent current (see GOST 30323-95, clause 3.1.1).
• Tav., s – response time of the protection device. The value is copied into the table from the corresponding field in the Protection device group.
• Iav., A – tripping current of the protection device. The value is copied into the table from the corresponding field in the Protection device group.

I set it to a nominal value of 250A and a multiplicity of 12In, and set the response time to 5s. According to the program's calculations, the short-circuit current came out to 2.9 kA and the program issued a conclusion that the device would not work... This conclusion is NOT CORRECT!

You have set the operating current (without taking into account the variation in characteristics) Iav.=250*12=3000 A or 3 kA. The program only considers what you give it. Since Iokz

If you look at the time-current characteristics of the VA53-41, it will work almost instantly!

The program does not have the ability to select the type of switch, so it is strange to listen to complaints that the program “didn’t realize” that the circuit breaker should trip.
It's obvious that you made a mistake. It was necessary to enter the operating current for a time of 5 seconds, then the program would calculate correctly.

And in 5 seconds it will work at 2kA thermal release from a heated state.

This means that this characteristic had to be introduced, and not 250 A at a 12-fold cutoff.

Then, for the sake of interest, I slightly changed the model of my circuit so that the current would be a little more than 3 kA - and, voila! The machine began to operate at any time of operation!

Of course, the program shows that the operation will occur within the time you specified. It should be noted that the standards indicate the maximum time for switching off the short-circuit current. Those. The shorter the response time, the better. The calculations should indicate the maximum permissible response time, in accordance with regulatory requirements. If, as a result, it turns out that the protection device will operate during this time, then regulatory requirements are being carried out.
Once again, the program does not count how long it will take for the operation to occur, but shows whether the short circuit will be disconnected within the time you specified or not.

The conclusion suggests itself - either in the “standard” version everything is so cut down, or in principle, when calculating, you can completely ignore setting the response time for the protective device.

In the standard version, only what is indicated in the description on the website is reduced, namely:

the functions for calculating short-circuit currents when powering consumers from an autonomous power plant have been reduced, and it is also impossible to export calculation results;

No more, no less.
The response time in some cases is not included in the calculations. Your case is an example of this. However, this time is indicated in the table of calculation results, and the expert (inspector) can immediately see that the regulatory requirements are met.
The response time plays an important role in determining the tripping of the protection device if a change occurs effective value periodic component of the short-circuit current over time. A typical case is a short circuit in a network powered by an autonomous diesel power plant.
Also, if a fuse with a fuse link is used as a protection device, then the response time cannot be avoided here either, because The tripping current of the fuse is determined by the response time.

I still don’t understand why, when determining the parameters of the transformer, the HV voltage can be selected only 10 kV.

The HV voltage can be selected from the one that is entered into the database for a specific transformer. The user can enter the data of the transformer with the required high side voltage and perform the short circuit calculation.

Thank you for your interest and your questions.