Smoothing device

Smoothing device (CS) - an element of constant electric current systems, designed to not pass the current of higher harmonics from the traction substation (TP) into the contact network (CS). They are connected between the positive (+) and negative (-) buses of the switchgear (RU) 3.3 kV ^[1] .

Content

1 General
2 Theory of work
3 Requirements for SU
4 SU schemes and their classification
- 4.1 Single-link resonant aperiodic smoothing device
- 4.2 Two-link resonant-aperiodic smoothing device of the West Siberian Railway
5 Elements of SU
6 Design
- 6.1 Note
7 Sources
8 Notes

General information

The voltage at the rectifier output u _d is ripple. It can be represented as the sum of the constant U _d component of the rectified voltage and the variable u _dk component, consisting of an infinite number of harmonics

u _d = U _d + u _dn

U_{dn}=\sum _{n=1}^{\infty }{u_{k}}

{\ displaystyle U_ {dn} = \ sum _ {n = 1} ^ {\ infty} {u_ {k}}}

U_{{dn}}=\sum _{{n=1}}^{\infty }{u_{k}}

,

where u _k is the harmonic voltage of the kth order.

With symmetrical supply voltages for 6-pulse converters (P), the ripple frequency is 50 × 6 = 300 Hz, for 12-pulse P: 50 × 12 = 600 Hz. With asymmetrical supply voltages, other harmonics appear that are multiples of a frequency of 100 Hz.

The variable component u _{d k} creates an alternating current i _{d k} in the "contact network - traction motor - rail" circuit, which in turn creates an alternating magnetic field F. This field induces electromotive force (EMF) in nearby wires of the communication line (LS), which creates a current i of the _{drug in the drug} , consisting of the same harmonics as u _{d k} . The consequence of this current is interfering effects (noise) on the telephone equipment.

With the use of multi-pulse converters on TP, the quality of the rectified voltage increases. However, with any rectification scheme in real conditions, a further reduction in the ripple of the rectified voltage is required, which is achieved by using smoothing devices.

u _dk → i _dk → Ф _≈ → EMF → i _hp

Theory of Work

The principle of operation of SU
The equivalent circuit of the traction network and SU

The constant component U _d creates a current I _d \\, which does not flow along the resonant circuits due to the presence of a capacitor C _k in them. The variable component u _dn creates a current i _dn , which can be represented in the form of two components:

$i_{dn}'$ ${\ displaystyle i_ {dn} '}$ - flows along the same chain as Id;
$i_{dn}''$ ${\ displaystyle i_ {dn} ''}$ - flows through the resonant circuits C _to - L _to .

  The variable component u _{dn is} distributed between the drop U in the resonant circuit - U _dnk and the drop U on the smoothing reactor L _d - U _dnp :

$U_{dn}=U_{dnk}+U_{dnp}$ ${\ displaystyle U_ {dn} = U_ {dnk} + U_ {dnp}}$

Therefore, ΔU in the resonant circuits u _dnK is simultaneously U, which creates an interfering alternating current i _dn 'in the traction network.

The smaller is u _dnк , the less is i _dn ', and the less is the influence of the traction network on drugs.

In an ideal CS, there should be u _dnk = 0, u _dnp = u _dn .

In real _CSs - u _dnк = 2%, and u _dnр = 98% of u _dn .

For ↓ u _dnк , apply ↑ S and ↓ l wires of the resonant circuits, for L _K and C _K ↓ R, and, especially, strive to achieve the best voltage resonance in the circuit ^{[ specify ]} .

Requirements for SU

voltage U _{dk with a} frequency of 100 Hz should not be more than 100 V;
psophometric U _ps voltage at the output of the smoothing device should be no more than 5 V for overhead communication lines and no more than 20 V for cable communication lines;
simplicity of the circuit;
minimal power losses in smoothing reactors;
The cost is minimal;
Reliability.

CS schemes and their classification

There are 3 varieties of SU:

Single-link resonant aperiodic smoothing device; ^[2]
Two-link resonant-aperiodic smoothing device of the West Siberian Railway;
Two-link resonant aperiodic smoothing device of VNIIZhT.

I do not use the latter at this time at traction substations of Russian Railways.

Single-link resonant aperiodic smoothing device

The SU is connected to the RU-3.3 kV buses using the QS disconnector. A PV voltmeter is connected to the RU buses, protected by a FU ₂ fuse.

The control system consists of a smoothing reactor LR 1 RBFA-U-6500/3250 U2 (concrete, filtered, aluminum, universal reactor, rated voltage 3.3 kV, rated current 6500 or 3250 A, for moderate climates, for installations with metal fences), a resonant circuit ' C 1- L 1 tuned to a frequency of 100 Hz, and a capacitive circuit C , which provides smoothing of higher harmonics.

To protect the control system, a fuse FU _{1 is used} . To control the operation of the SU, a current transformer TA (TChS-2-75 / 5U2) is installed. The transformer secondary circuit includes an ammeter and a current relay of the RT-40/10 type. The latter is necessary to signal the maintenance personnel about the increase in current in the control system with a time delay of 1-2 s. The response current for this alarm is 60 A at a non-connect substation and 80 A at a butt.

Two-link resonant aperiodic smoothing device of the West Siberian Railway

Two-link resonant-aperiodic smoothing device of the West Siberian Railway

In a two-link control system, three resonant circuits L ₁ - C ₁ , L ₂ - C ₂ , L ₃ - C _{3 are} tuned to frequencies of 100, 200, 300 Hz and form with the reactor LR 1

RBFA-U-6500/3250 inductance LR 1 = 5mH the first link. The capacitance C together with the reactor LR 2 with an inductance of 3 mH form the second link

Control Elements

The control system includes smoothing reactors LR , resonant circuits, equipped with capacitors C and inductors L , as well as capacitive circuits.

RBFAU-3.3-6500 SU reactor

The reactor is the main element of the control system and is designed to reduce the interfering effect of harmonic components on communication devices. However, the smoothing effect of the reactor is small and it is used in combination with capacitance and inductance. The RBFA-6500/3250 reactor has 4 parallel branches and can carry a load of 3250 or 6500 A. without overheating.

Inductors

Inductors are an integral element of the traction substation control system. They are connected in series with capacitors and form circuits tuned to resonance at frequencies of 300, 600, 900 and 1200 Hz. Coils are made of stranded copper wire.

High voltage capacitor

Capacitors are the second component of the control system. Capacitors must have a paper impregnated dielectric and operate for a long time at a nominally rectified voltage of 3300 V in a resonant circuit.

Design

Constructive arrangement of the elements of the smoothing device
The design of the smoothing device

The design of the smoothing device ^[3]

Note

Inductors are made of copper wire PR-500 of various sections and number of turns. FMT4-12 paper-oil capacitors with a capacity of 12 microfarads designed for a voltage of 4 kV are used.

Resonant coils and capacitors are installed in separate rooms of the closed part of the transformer substation or in metal cabinets.

Large-sized reactors are installed in chambers with metal fences.

To measure psophometric voltage at the output of the control system at traction substations, I install the medical device. ^[four]

Sources

All about capacitors. Article: Classification and Conventions of Condensers [Electronic resource]

URL : http://www.amfilakond.ru/article3.shtm (unavailable link) (accessed 04.04.15);

Traivas M. D. Higher harmonic rectified voltage and their decrease in DC traction substations. - M., "Transport", 1964. 100s .;
B. S. Barkovsky, G. S. Magay, V. P. Matsenko and others; Ed. M. G. Shalimova. Twelve-pulse semiconductor rectifiers of traction substations. - M .: Transport, 1990.-127s;
Pochaivets V. S. Electrical substations: Textbook. for technical schools and colleges transp. - M .: Zheldorizdat, 2011 .-- 512 s. ISBN 5-94069-012-2 ;
Bader M.P. Electromagnetic compatibility / Textbook for universities of railway transport.-M.: UMK MPS, 2002.-638с. ISBN 5-89035-065-X
Nizov A.S. Electromagnetic compatibility. Methodical manual with assignments, guidelines and reference materials. - Yekaterinburg, 2006. - 68s.
CE-39. Instructions for maintenance and repair of traction substation equipment, power points and sectioning of electrified railways;
Pochaivets V.S. Electrical Equipment and Appliances of Electrical Substations: A Textbook for University Students, Technical Schools, Colleges, and Students at Educational Institutions transport, providing initial vocational training.-M.: UMK MPS of Russia, 2002.-52с. ISBN 5-89035-049-8 ;
Electric Networks [Electronic resource]: URL: http://leg.co.ua/arhiv/podstancii/elektrosnabzhenie-elektrificirovannyh-zheleznyh-dorog-11.html ;
http://lokomo.ru/ [Electronic resource]: URL: http://lokomo.ru/elektrosnabzhenie/sglazhivayuschie-ustroystva.html
Bey Yu. M., Mamoshin R.R., Pupynin V.N., Traction substations / Textbook for high schools. transport. - M .: Transport, 1986 - 319 p .;
Smoothing reactors for DC traction substations. Safety standards. TsEPZ-2003. Moscow.

Notes

↑ Pochaivets V.S. Electrical substations. - Zheldorizdat, 2011 .-- 512 s.
↑ Shtin A.N. UrGUPS. Selection of switchgear equipment for traction and transformer substations. - Yekaterinburg: UrGUPS, 2009 .-- S. 68.
↑ Pochaivets V.S. Electrical equipment and apparatus of electrical substations. - UMK Ministry of Railways of Russia. - 2002. - 52 p. - ISBN ISBN 5-89035-049-8 .
↑ CE-39. Instructions for maintenance and repair of traction substation equipment, power points and sectioning of electrified railways.

[1] Pochaivets V.S. Electrical substations. - Zheldorizdat, 2011 .-- 512 s.

[2] Shtin A.N. UrGUPS. Selection of switchgear equipment for traction and transformer substations. - Yekaterinburg: UrGUPS, 2009 .-- S. 68.

[3] Pochaivets V.S. Electrical equipment and apparatus of electrical substations. - UMK Ministry of Railways of Russia. - 2002. - 52 p. - ISBN ISBN 5-89035-049-8 .

[4] CE-39. Instructions for maintenance and repair of traction substation equipment, power points and sectioning of electrified railways.