RU2537851C2 - Method for controlling ice-crusted overhead transmission lines - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention refers to a method for ice crust melting on overhead high-voltage transmission lines requiring no customer curtailment. A reactive power source (RPS) is connected to the overhead transmission line of 6(10) kV, wherein the ice crust melting is required, so that to direct a generated reactive power flow towards an active power flow in the overhead line. This voltage distribution along the overhead line is more uniform at the same current as compared to an equal active and reactive power flow, and enables taking the measures to control ice crusts requiring no customer curtailment. The RPS power is specified so that to allow the overhead line current according to the assembled circuit of the ice crust melting to melt the ice crust (or to heat the overhead conductors up to avoid icing). The presented method can be implemented by using both the RPSs already installed in the distribution networks (capacitor banks, synchronous compensators, static reactive power compensators), and the new RPSs (including relocatable (mobile) ones).

EFFECT: invention provides the ice crust melting on the overhead transmission lines requiring no customer curtailment.

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Description

The invention relates to the electric power industry, and more specifically to methods of melting ice on wires of air high-voltage power lines (power lines) without disconnecting consumers.

Ice smelting (thermal method) is currently the main measure to prevent icing accidents in electrical networks. It allows you to remove ice on dozens of kilometers of lines within 0.5 ... 1 hour, prevent dangerous overload and eliminate the dance of wires.

Recently, ice melting methods have been developed according to the method of redistributing loads and applying currents.

In the patent CN 101615772 (published on December 30, 2009), a method for using reactive power flow for melting ice on air lines (OHL) is implemented. According to this method, for smelting ice, it is necessary: firstly, to disconnect the overhead line on which ice should be smelted, secondly, to disconnect the reactive power compensation device from the substation buses from which the overhead lines depart, and thirdly, to connect the reactive power compensation device of one substation to the bus of another substation through the overhead line, on which ice should be melted, while the reactive power flow allows ice to be melted.

The disadvantage of this method is the need to take the line out of operation, which is possible without disconnecting the network consumers only if it is redundant (for example, for double-circuit lines). In networks of 6 (10) kV for agricultural purposes, as a rule, lines (feeders) are single-circuit with the possibility of supplying many consumer step-down substations from the main section of the line using the so-called solders (branches) connected at different points of this main section. This leads to the need to disconnect feeder consumers that do not have backup power.

The main task, the solution of which is claimed by the claimed method, is the smelting of ice on overhead lines with the preservation of power supply to consumers.

The technical result of the invention is to melt ice on a HVL of 6 (10) kV while maintaining power supply to the consumers who are eating from it.

The specified technical result is achieved by the fact that in the method of dealing with icing on overhead power lines, which consists in increasing the current along these lines by artificially creating an additional reactive power stream by connecting a reactive power source to one end of the line, according to the invention, the reactive power source is connected to the end of the 6 (10) kV feeder line made by single-circuit overhead lines without disconnecting the feeder from the power substation with a simultaneous change in position regulator transformer under load at this substation so that the stress levels along the highway remain valid for the fed power consumers. In this case, the source of reactive power can be movable.

The proposed method is illustrated by drawings. Figure 1 presents the structural diagram of the network, where 1 is the power center; 2 - electricity consumer with an active load power P; 3 - source of reactive power (IRM); Q is the oncoming flow of reactive power. Figure 2 shows a diagram of the distribution of currents along a feeder, consisting of 5 nodes, in the mode of melting ice. Figure 3 presents the diagrams of the stress distribution along the feeder, consisting of 5 nodes, in normal mode and in the mode of melting ice. Figure 4 shows the structural diagram of the network, where KA - switching devices.

, (1)The way to deal with icing on overhead power lines is as follows. To the feeder 6 (10) kV, made by a single-circuit air line, on which it is necessary to melt ice, IRM 2 is connected in order to create an additional reactive power flow directed counter to the active power flow along the overhead line (Fig. 1). An IRM can be an adjustable or unregulated capacitor bank (BC), a synchronous compensator or a synchronous motor, a static thyristor compensator. In this mode, the voltage distribution along the line is more uniform at the same current, compared with the regime of the same direction of active and reactive power. The power of the IRM Q _{IRM is} selected so that the current flowing along the overhead line with the assembled ice melting circuit allows the ice to be melted (or to heat the overhead lines to prevent icing), and is determined by the following expression: $$Q_{{}_{{}_{\mathrm{AND}RM}}}=\sqrt{S_{Pl(PRed)}^2-R_H^2}+Q_H$$

, (one)

where S _{PL (pre)} is the power of melting ice (preventing icing), depending on the amount of current required to melt ice (preventing icing);

P _H - active load power;

Q _H = P _H · tgφ is the reactive power of the load.

Expression (1) is valid both for overhead lines with a load concentrated at the end of this line, and for overhead lines with a load distributed along it. In the second case, the current along the line will be distributed unevenly. The current will take on the greatest importance in the area adjacent to the IRM, therefore, the power of the IRM for smelting ice should be determined based on the power flow in the head section. The power of the IRM for melting ice with distributed consumption coincides with the power of the IRM for melting ice with concentrated load, taking into account that the active power of the head section is identical for both cases.

To implement the described approach, one can use both the IRMs already installed in the distribution networks and the new IRMs, which will be installed taking into account the possibility of ice melting.

For melting ice on the main sections of ringing feeders of 6 (10) kV, stationary IRMs connected to sections of 6 (10) kV buses supplying these feeders of substations can be used. In this case, the power supply of such a section of tires is carried out from another section of the tires of the supply substation through a ring feeder, on the mains of which ice is smelted.

For OHL with one-sided power supply, IRM for ice melting is installed at the end of this OHL. In this case, it is possible to use movable (mobile) IRMs, for example, movable BCs. In particular, the BC is moved using trucks (the use of a truck crane together with a truck; or consideration of the possibility of transportation at the stage of creation of the BC, using elements in its design that allow it to be moved as a “trailer” to freight vehicles). At the same time, in the autumn-winter period mobile BCs are used to conduct ice melting activities, and in the summer they can be used for their intended purpose (reactive power compensation). The use of “movable” or “mobile” BCs to compensate for reactive power is effective, since during operation, as a rule, changes occur both in the network circuit and in the loads of its nodes, which affect the efficiency of BC use.

In the context of Smart Grid implementation, it is advisable to automatically reconfigure the network to increase the active power overflow along the overhead line, which requires ice melting, which reduces the required capacitor bank power and makes the voltage distribution in the network more uniform during ice melting.

In order to maintain acceptable voltage levels along the mains for power supply to the supplied consumers during ice melting, voltage regulation is carried out at the substation, from which the overhead line departs. Maximum voltage deviations on consumer tires in accordance with GOST 13109-97 must not exceed ± 10%. When installing the IRM at the end of line 4, the voltage at the consumer will increase and may exceed the permissible value. To reduce it to an acceptable level, it is possible to regulate the voltage in the power center (CPU) using the on-load tap-changer of the supply transformer. However, the minimum voltage value in the CPU will be determined by consumers nearby. Thus, to ensure acceptable voltage deviations among consumers, the maximum voltage loss in the line should not exceed a certain value ΔU _MAX . The voltage drop depends both on the values of the power fluxes and on the OHL parameters (resistivities and line lengths). In this regard, there is a limiting value of the line length at which the tolerance of voltage deviations from consumers will be maintained depending on the power flows along the overhead line and the brand of wires from which it is made. So, the maximum length of overhead lines with U _nom = 10 kV, made by AC-70 wire, with active power overflow R _H in the range from 0 to 1.8 MW, on which ice can be melted while maintaining power supply to consumers, is in the range from 8.35 km and up to 12.8 km.

Example 1

Consider a feeder with U _nom = 10 kV, with a load concentrated at the end of the line, R _n = 1.2 MW, Q _n = 0.9 M _var , made of AC-70 wire, 10 km long, on which ice should be melted (or to prevent the formation of ice) at a wind speed of ν = 4 m / s and an air temperature of t = -5 ° C. For these conditions, the current of ice melting I _PD = 320 A. The power of the IRM necessary for melting the ice is determined by (I): Q _IRM ≈ M _var . Current to prevent the formation of ice for these conditions I _pre = 220 A.

The power of the IRM necessary to prevent the formation of ice is also determined by (I): Q _IRM 3.6 M _var . When installing IRM of such capacities at the end of the line (at the consumer), the current in the line reaches the required values (melting ice or preventing its formation), and the voltage at the consumer can be kept in the required range by regulating the voltage in the CPU.

Example 2

Consider a feeder with 5 transformer substations (TP) with full power in the head P = 1.73 MW and cosγ = 0.9, the lines of which are made of AS-70 brand wire and have a total length of 5 km.

For ice melting by the oncoming reactive power flow, an IRM with a power of Q _IRM = 6M _var is required.

When installing an IRM of such power, ice melting is feasible along the entire feeder, while the maximum current in the line does not exceed the maximum permissible current value for this line. The plot of the distribution of currents along the line in the mode of melting ice is shown in figure 2.

Figure 3 shows the diagrams of the stress distribution along the feeder feeding 5 TP, in normal mode and in the mode of melting ice. As follows from the voltage diagrams, to ensure normalized voltage deviations among consumers, it is necessary to reduce the voltage in the CPU using the on-load tap-changer of the supply transformer in the ice melting mode.

Example 3

Figure 4 shows a feeder with 5 TP (highlighted with a dash-dotted line), on which it is necessary to take measures to prevent the formation of ice, with full power in the head P = 1.73 MW and cosγ = 0.8, the lines of which are made of AC brand wire -70 and have a total length of 5 km. At the end of the feeder, it is possible to connect an IRM with a power of Q _IRM = 3.6 M _var . However, the capacity of this IRM is not enough to conduct anti-icing measures. For this feeder, it is possible to increase the flow of active power by attaching an additional load. The additional load power is selected in such a way that the total active power flow P _sum and the reactive power flow Q counter to it at the head section of the feeder create a current of the required value. In order to conduct heating of the wires of this feeder, it is necessary to connect an additional load with a power of P _add = 1.3 MW, while the voltage at the consumers is within acceptable limits.

Claims (2)

1. The method of dealing with icing on overhead power lines, which consists in increasing the current along these lines by artificially creating an additional reactive power stream by connecting a reactive power source to one end of the line, characterized in that the reactive power source is connected to the end of a single-circuit air lines of the feeder 6 (10) kV without disconnecting the feeder from the supply substation while changing the position of the regulator under the load of the transformer in this sub Antium so that stress levels along the highway remain valid for the fed power consumers. 2. The method according to claim 1, characterized in that the reactive power source can be relocatable.

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