MOBILE EQUIPMENT FOR MELTING THE ICE CRUST

ON 110 – 220 KV OVERHEAD LINES1

É. E. Son,2 É. Kh. Isakaev,2 A. S. Tyuftyaev,2 D. V. Tereshonok,2 B. M. Antonov,2

V. K. Korolev,2 V. B. Mordynskii,2 and P. A. Konovalov2

Translated from Élektricheskie Stantsii, No. 2, February 2013, pp. 46 – 49.

Mobile equipment for melting the ice crust on the conductors and lightning-protection cables of overhead

electric power lines is described, as one of the most promising methods of combating the destruction of the

supports and of the electric power lines themselves due to ice-wind loads.

Keywords: electric power lines; ice-crust melting; mobile equipment; melting current.

Damage to overhead electric power lines due to deposi-

tion of ice is the most difficult in its aftereffects, since breaks

in the conductors and cables, damage to the equipment and

insulators, and even the supports of the overhead lines are

possible. Periodic interruption of electrical supplies to the re-

gions and the restoration of the overhead lines, damaged by

ice, involve considerable capital costs, as well as much effort

by electrical power engineers [1].

The problem of preventing ice emergencies in the elec-

tric networks is urgent for the majority of regions in Russia.

The main method of combating ice is melting it by heating

the conductors with alternating or direct current.

Melting of the ice using alternating current requires a

considerable amount of power from the power supply (up to

several hundreds of MV · A) [1, 2], since the line conductors

have considerable inductance, and the total source power is

increased due to the reactive component.

In cases when the ice cannot be melted by an alternating

current using the power of the substation transformers and

specified nominal voltages, one must melt the ice using di-

rect (rectified) current [3]. To do this, special converters are

set up at the substations. The power of these converters is

also considerable — tens of megawatts. However, often it is

not required to heat the wires over the whole extent of the

overhead line, since in many network regions the icing of the

overhead line is local. In such cases it is better to use mobile

devices to clean the conductors and lightning-protection ca-

bles from the ice crust on individual sections of the overhead

lines [1, 4], in particular, mobile equipment for melting the

ice (MEMI).

The construction and design of the MEMI is chosen tak-

ing into account the limitations on the weight and size of ex-

isting diesel electric power stations (diesel generator equip-

ment) and the complex operating conditions, due to the diffi-

culty of gaining access to the overhead line, on which

operations must be carried out, the reduced temperature and

increased humidity of the air, as well as the wide range of

electrical parameters of overhead lines. Inaccessible parts of

the overhead line make it necessary to use an MEMI on an

automobile chassis with off-the-road potential. The electrical

equipment is placed in a container, since the control system

of the diesel generator and the converter needs to operate at a

temperature no lower than 1 – 2°C. Due to the lack of a suit-

able model of such an automobile chassis, an automatic hoist

and container with the power equipment of the MEMI are

placed on two separate automobiles. This optimizes the pro-

cess as a whole, since during the melting time the automatic

hoist is able to return to the point where the short is placed, in

order to remove it (Fig. 1). In addition, the automatic hoist or

the diesel generator equipment can be used separately for an-

other purpose.

Power Technology and Engineering Vol. 47, No. 2, July, 2013

155

1570-145X�13�4702-0155 © 2013 Springer Science + Business Media New York

1 This work was supported financially by the Ministry of Education and

Science of the Russian Federation (State Contract No. 16.516.11.6095.

2 Joint Institute for High Temperatures of the Russian Academy of

Sciences, Russia.

Short Lightning cable Line conductor

Car hoist MEMI

2 km

Fig. 1. Sketch illustrating the use of MEMI for melting ice.

An electrical block diagram of the MEMI and the circuit

for connecting it to the conductors and cable of the overhead

line are shown in Fig. 2.

The electrical parameters of the MEMI are determined

both by the means by which the ice is melted and the resis-

tance of the conductors of the different types of overhead

lines, and by the possibilities of transporting the MEMI. In a

standard 20-foot container, taking into account the arrange-

ment of the converter, one can arrange diesel generator

equipment with a power of not more than 300 kW, which de-

termines the choice of the main electrical parameters of the

MEMI.

When melting the ice crust on conductors with rectified

current, as a rule, two circuits for connecting the conductors

to the rectifier are employed: “phase – phase” and “phase –

two-phase.” In the first version the overall melting time is

less while in the second the required power is less. In our

opinion, as it applies to the MEMI, the second version is

preferable.

The permissible ice melting currents and the duration of

the melting for specific grades and cross sections of the con-

ductors are given in [1]. Preliminary calculations showed

that acceptable (up to 30 kW) active power of the MEMI is

obtained if the ice is melted in a 30-min session on a 2-km

section of 110 – 220 kV overhead lines (with AS120 –

AS500 grade conductors) using the “phase – two-phase”

scheme (Table 1).

Choice of the electrical circuit of the MEMI. When

choosing the power source one must consider the total power

consumed by the MEMI during melting, which depends on

the current conversion circuit. We considered two versions:

circuit 1 — a controlled thyristor bridge rectifier and circuit

2 — an uncontrolled bridge rectifier with a pulse-width cur-

rent regulator at the output. The calculated parameters of the

MEMI for these circuits are presented in Table 2.

For the circuit with the converter with a pulse-modulated

regulator, a power source of considerably less power is re-

quired. Using a circuit developed by the Elektrovypryamitel’

Company we constructed a converter for the MEMI, a block

diagram of which is shown in Fig. 3.

The bridge rectifier provides control, but operates with

minimum control angle, i.e. with characteristics close to the

characteristics of an uncontrolled rectifier, and, in an emer-

gency, can perform the function of quick-acting protection.

Since the maximum voltage of the rectifier (about 500 V) is

insufficient to provide a 30-min current for melting the ice

crust on the lightning cables, in this mode of operation the

voltage on the rectifier is supplied through a voltage-boost-

ing autotransformer 5.

We chose the Gesan DPA 400E diesel electric plant, hav-

ing a power of 288 kW (360 kV · A) with an output line volt-

age of 400 V as the power supply.

The assembly of the electrical equipment on the autocon-

tainer cart is shown in Fig. 4.

The wheel 6 for winding and unwinding the cables is ro-

tated by an electric drive, consisting of a worm reductor 9

and a dc electric motor 10, supplied from the on-board auto-

mobile network.

156 É. E. Son et al.

1 2

A

B

C

5

3 4

6

Cable

Fig. 2. Electrical block diagram and circuit for connecting the

MEMI to the overhead line: 1, 2, terminals for connecting the cur-

rent-conducting cables and the short; 3, the diesel generator equip-

ment; 4, an automatic switch; 5, a converter; 6, a switch for choosing

the parts of the overhead line where the ice is to be melted.

TABLE 1. Calculated Electrical Parameters for a 30-min Melting Session

Calculated parameter

Grade of conductor and lightning cable

AS120 AS150 AS185 AS240 AS300 AS400 AS500 S50 S70

DC electrical resistance R, Ù�km 0.244 0.204 0.159 0.122 0.096 0.073 0.058 ~2.8 ~2

Resistance of 2 km of wire 2R, Ù 0.488 0.408 0.318 0.244 0.192 0.146 0.116 ~5.6 ~4

Resistance of the conductors in version 1 R1 = 4R, Ù 0.976 0.816 0.636 0.488 0.384 0.292 0.232 5.76 – 5.6 4.08 – 4.04

Resistance of the conductors in version 2 R2 = 3R, Ù 0.732 0.612 0.477 0.366 0.288 0.219 0.174 5.76 – 5.6 4.08 – 4.04

Melting current (30 min) Im, A 565 657 747 863 890 1045 1125 100 140

Melting voltage in version 1 Um = R1Im, V 551 536 475 421 330 305 261 ~570 ~560

Active melting power in version 1 Pm = UmIm, kW 311 352 355 363 294 319 294 57 78

Melting voltage in version 2 Um = R2Im, V 414 402 356 316 256 229 196 ~570 ~560

Active melting power in version 2 Pm = UmIm, kW 234 264 266 273 228 239 220 57 78

Note. Version 1 is with the conductors connected to the rectifier using the “phase-phase” scheme, and version 2 is with the conductors con-

nected in the “phase – two-phase” scheme.

CONCLUSIONS

We have constructed mobile equipment for melting the

ice crust on conductors and the lightning cables of 110 –

220 kV overhead lines, which enables the ice on lengths of

not less than 2 km to be melted in a time of not more than

30 min per phase.

REFERENCES

1. F. D’yakov, A. S. Zasypkin and I. I. Levchenko, Prevention and

Removal of Ice Damage in Power System Electric Networks [in

Russian], Yuzhenergotekhnadzor, Pyatigorsk (2000).

2. RD 34.20.504–94. Routine Instruction on the Use of 35 – 800 kV

Overhead Electric Power Lines [in Russian], Izd. NTs ÉNAS,

Moscow (2003).

3. MU 34-70-028–82. Systematic Instructions on the Melting of Ice

Using Direct Current [in Russian], Soyuztekhenergo, Moscow

(1983).

4. Results of the Meeting of HTS RAO “EES Rossii,” 19 – 20 Febru-

ary 2002. Order No. 218 RAO “EÉS Rossii” of 18 April 2002 [in

Russian].

Mobile Equipment for Melting the Ice Crust on 110 – 220 kV Overhead Lines 157

TABLE 2. Calculated Electrical Parameters of the MEMI

Electrical parameters for a 30-min session

of ice melting

Grade of conductor and of the lightning protection cable

AS120 AS150 AS185 AS240 AS300 AS400 AS500 S50 S70

Resistance of the conductor (cable), Ù 0.732 0.612 0.477 0.366 0.288 0.219 0.174 ~5.7 ~4.05

Melting current (30 min), A 565 657 747 863 890 1045 1125 100 140

Melting voltage Um, V 414 402 356 316 256 229 196 ~570 ~560

Active melting power Pm, kW 234 264 266 273 228 239 220 57 78

Circuit 1

Rectifier current, A 565 657 747 863 890 1045 1125 100 140

Rectifier voltage Ur = Um, V 414 402 356 316 256 229 196 500 500

Total source power (fundamental harmonic)

S U I( ) .min

1 3 0 82� 4

m, kV · A

321 373 424 490 506 594 640 50 70

Circuit 2

Rectifier voltage Ur, V 500 500 500 500 500 500 500 500 500

Rectifier current Ir = Pm�Ur, A 468 528 532 545 456 480 441 88 123

Total source power (fundamental harmonic)

S U I( ) .min

1 3 0 82� 4

r, kV · A

266 300 302 310 260 273 250 50 70

3

21

4

6

5

7

8 9

10

400 V

from

DGE

Load

Fig. 3. Block diagram of the converter circuit: 1, fifth and seventh

harmonic filters; 2, current measuring transformers; 3, the electric

generator automatic control system; 4, a switch for choosing the

rectifier voltage; 5, a voltage-booster autotransformer; 6, current-

limiting reactors; 7, a controlled thyristor rectifier; 8, an LC-filter;

9, a transistor switch; 10, a backward diode.

1 2 3 4

6

1 2 3 4 10 9 7 6

8

5

6068

9393

3970

2000

850

5

2550

Fig. 4. Arrangement of the MEMI equipment on the truck: 1, the

autocontainer cart; 2, the transport container; 3, the diesel electric

plant; 4, the converter; 5, the switch for choosing the elements; 6, a

reel for winding the cable in its bearing supports 7 and 8; 9, a worm

reductor; 10, a DC electric motor.