JPS6321152Y2

JPS6321152Y2 -

Info

Publication number: JPS6321152Y2
Application number: JP2332481U
Authority: JP
Priority date: 1981-02-23
Filing date: 1981-02-23
Publication date: 1988-06-10
Also published as: JPS57139234U

Description

[Detailed explanation of the idea]

本考案はアーク炉や整流器などを負荷とする高
調波発生源の多い交流電源系統における高調波フ
イルタの過電流保護装置に関するものである。高調波発生源であるサイリスタ変換装置が接続
される鉄鋼設備等の特別高圧や高圧の交流電源系
統には、高調波フイルタが採用されている。また
発生高調波電流の次数は５次，７次，11次，13次
…等である。第１図にこれらの交流電源系統の一例を示す。
第１図においてCB１は高調波フイルタ系統用の
しや断器、CT５は５次調波フイルタの変流器、
OC５は５次高調波フイルタ系統保護用の過電流
継電器、Ｃ５およびＬ５は５次調波フイルタのコ
ンデンサとリアクトルであり、以下同様にCT７，
OC７，Ｃ７，Ｌ７は７次調波用、CT１１，OC
１１，Ｃ１１，Ｌ１１は11次調波用、CT１３，
OC１３，Ｃ１３，Ｌ１３は13次調波用である。またＭは直流電動機、THYは高調波の発生源
であるサイリスタ変換装置、Ｔはサイリスタ用変
圧器、CB２はその交流電源系統用しや断器であ
る。CB３は高調波を発生しない電源系統用のし
や断器である。高調波フイルタの保護装置としては電気的に検
出するものと、コンデンサの圧力検出や容器変形
を検出する機械的なものとがあり、一般に両方を
併用することが多い。電気的検出装置としては一
般に過電流継電器の採用が多い。第２図に第１図に対応する高調波フイルタの過
電流保護回路の一例を示す。制御電源母線Ｐから
OC５の過電流で動作する接点OCと短絡電流で動
作する瞬時動作接点INSTを介してCB１の引外
コイルTCの一端に接続され、TCの他端は制御電
源母線Ｎに接続されている。同様にOC７，OC１
１，OC１３，CB１の引外コイルTCに接続され
る。第２図で高調波フイルタが過電流になるとOC
が動作し、短絡事故ではINSTが動作してしや断
器CB１を引外す。この過電流で動作する接点OCの動作点は高調
波フイルタの定格電流すなわち（基本波電流）²＋
（高調波電流）²を基にして整定される。基本波電
流は商用周波数のときの電流であり、この電流Ｉ
は抵抗をＲ、リアクトルをＬ、コンデンサをＣ、
線間電圧をＥとすると三相直列回路であるので、
The present invention relates to an overcurrent protection device for a harmonic filter in an AC power supply system with many harmonic generation sources whose loads include arc furnaces and rectifiers. Harmonic filters are employed in special high-voltage or high-voltage AC power systems such as steel equipment to which thyristor converters, which are harmonic generation sources, are connected. Further, the orders of the generated harmonic currents are 5th, 7th, 11th, 13th, etc. Figure 1 shows an example of these AC power supply systems.
In Figure 1, CB1 is the shield breaker for the harmonic filter system, CT5 is the current transformer for the 5th harmonic filter,
OC5 is an overcurrent relay for protecting the 5th harmonic filter system, C5 and L5 are the capacitor and reactor of the 5th harmonic filter, and CT7,
OC7, C7, L7 are for 7th harmonic, CT11, OC
11, C11, L11 is for 11th harmonic, CT13,
OC13, C13, and L13 are for the 13th harmonic. Further, M is a DC motor, THY is a thyristor converter which is a harmonic generation source, T is a thyristor transformer, and CB2 is a circuit breaker for the AC power system. CB3 is a power supply system disconnector that does not generate harmonics. There are two types of protection devices for harmonic filters: electrical detection devices and mechanical protection devices that detect capacitor pressure and container deformation, and both are often used together. Generally, overcurrent relays are often used as electrical detection devices. FIG. 2 shows an example of an overcurrent protection circuit for a harmonic filter corresponding to FIG. 1. From control power bus P
It is connected to one end of the tripping coil TC of CB1 via a contact OC that operates with an overcurrent of OC5 and an instantaneous operation contact INST that operates with a short circuit current, and the other end of TC is connected to a control power supply bus N. Similarly OC7, OC1
1, OC13, connected to tripping coil TC of CB1. In Figure 2, when the harmonic filter becomes overcurrent, the OC
operates, and in the event of a short-circuit accident, INST operates and trips the breaker CB1. The operating point of the contact OC that operates with this overcurrent is the rated current of the harmonic filter, that is (fundamental current) ² +
(Harmonic current) Set based on ² . The fundamental wave current is the current at the commercial frequency, and this current I
is the resistance R, the reactor L, the capacitor C,
If the line voltage is E, it is a three-phase series circuit, so

【式】となる。また高調波フイルタは吸収する各調波に対し、
コンデンサとリアクトルを共振させるように定数
が選ばれ、共振時はωL＝１／ωcとなることから一般に基本波電流より高調波電流の方が大きい。あ
る設備の基本波電流と高調波電流の一例を第１表
に示す。[Formula] becomes. In addition, for each harmonic that a harmonic filter absorbs,
The constant is selected so that the capacitor and the reactor resonate, and at resonance, ωL = 1/ωc, so the harmonic current is generally larger than the fundamental current. Table 1 shows an example of the fundamental wave current and harmonic current of a certain equipment.

【表】一方高調波フイルタはコンデンサがあるため系
統の力率改善の役目もする。一般には第１図の
CB３のような高調波を発生しない系統も並列に
接続されているので、高調波発生源であるTHY
が停止しても高調波フイルタは系統に接続されて
いる。このような場合は、高調波フイルタには基本波
電流のみが流れるので、前記のように過電流で動
作する接続OCを、高調波フイルタの定格電流を
基準にして整定した場合は基本波電流の数倍、例
えば前記の一例によると約４〜５倍以上でなけれ
ば検出できない。従つて基本波電流時に高調波フ
イルタの異常を検出するには基本波電流を基準に
して整定しなければならない。以上のように高調波フイルタに流れる電流は
THYの運転停止により変化し、基本波電流と高
調波電流の大きさに差があることから従来方法で
は基本波電流時の過電流保護ができないという問
題があつた。本考案は前記の問題を考慮してなされたもの
で、高調波フイルタに基本波電流のみが流れてい
る場合にも過電流保護ができる高調波フイルタの
過電流保護装置を提供するものである。以下本考案を第３図および第４図に示す一実施
例に基づいて説明する。第３図は本考案を用いた
電源系統を示したもので、第１図に対し基本波電
流の過電流で動作する第２の過電流継電器が追加
されている。すなわちOC５Ａは５次調波フイルタの第２の
過電流継電器、以下同様OC７Ａは７次、OC11A
は11次、OC１３Ａは13次の第２の過電流継電器
である。次に第４図に本考案の過電流保護回路を示す。
第４図は第２図に対し基本波電流の過電流で動作
する第２の過電流継電器OC５Ａ〜OC１３Ａとサ
イリスタ変換装置THYが停止中であることを示
す接点THY−１ｂおよびサイリスタ変換装置の
交流電源系統用しや断器CB２が開の時閉じる補
助接点CB２−１ｂを追加したものである。第４図において制御電源母線Ｐから第２の過電
流継電器OC５Ａ〜OC１３Ａの過電流で動作する
接点OCAを並列に接続し、THYの停止中に閉じ
る接点THY−１ｂおよびCB２が開の時閉する補
助接点CB２−１ｂを介して高調波フイルタ系統
用しや断器CB１の引外コイルTCの一端に接続
し、TCの他端は制御電源母線Ｎに接続される。一方第１の過電流継電器OC５〜OC１３の高調
波電流時に過電流で動作する接点OCは制御電源
母線Ｐから並列に接続されCB１の引外コイルTC
の一端に接続される。またOC５〜OC１３の短絡
事故の際動作する接点INSTは制御電源母線Ｐか
らそれぞれ並列に接続されCB１の引外コイルTC
の一端に接続される。第４図において高調波の発生源であるサイリス
タ変換装置THYが運転中に過電流になつたとき
は、高調波フイルタの定格電流を基準として整定
されているOC５〜OC１３の過電流接点OCが動
作してＰ→OC→TC→Ｎの回路が構成されてCB
１を引外し、またOC５〜OC１３の短絡事故の際
はOC５〜OC１３のINSTが動作してCB１を引
外すのは従来と同様である。一方、サイリスタ変換装置THYが停止中の場
合、または、CB２が開いているときは高調波は
発生せず、高調波フイルタには基本波電流のみが
流れる。この時はTHYが停止中の信号THY−１ｂま
たはCB２の補助接点CB２−１ｂが閉じており、
基本波電流時に過電流になつた時は基本波電流値
を基準として整定されている第２の過電流継電器
OC５Ａ〜OC１７Ａの過電流で動作する接点
OCAが動作してＰ→OCA→THY→１ｂ→TC→
ＮまたはＰ→OCA→CB２→１ｂ→TC→Ｎの回
路が構成されてCB１を引外す。以上説明したように本考案によれば高調波フイ
ルタを基本周波数に対する力率改善にも使用して
いる場合、基本周波数に対する過電流保護もでき
る高調波フイルタの過電流保護装置を得ることが
できる。[Table] On the other hand, since harmonic filters have capacitors, they also play a role in improving the power factor of the system. In general, Figure 1
Since systems that do not generate harmonics such as CB3 are also connected in parallel, THY, which is a source of harmonics,
Even if the system stops, the harmonic filter remains connected to the grid. In such a case, only the fundamental current flows through the harmonic filter, so if the connected OC that operates with overcurrent is set based on the rated current of the harmonic filter, the fundamental current will be It cannot be detected unless it is several times larger, for example, about 4 to 5 times or more according to the above example. Therefore, in order to detect an abnormality in the harmonic filter when the fundamental wave current is present, it is necessary to set the fundamental wave current as a reference. As shown above, the current flowing through the harmonic filter is
Due to the difference in magnitude between the fundamental wave current and the harmonic current, which changes when THY is stopped, the conventional method has had the problem of not being able to provide overcurrent protection at the time of the fundamental wave current. The present invention has been devised in consideration of the above-mentioned problems, and provides an overcurrent protection device for a harmonic filter that can provide overcurrent protection even when only the fundamental current flows through the harmonic filter. The present invention will be explained below based on an embodiment shown in FIGS. 3 and 4. FIG. 3 shows a power supply system using the present invention, in which a second overcurrent relay that operates with an overcurrent of the fundamental wave current is added to FIG. 1. In other words, OC5A is the second overcurrent relay of the 5th harmonic filter, OC7A is the 7th overcurrent relay, and OC11A
is the 11th order overcurrent relay, and OC13A is the 13th order second overcurrent relay. Next, FIG. 4 shows the overcurrent protection circuit of the present invention.
Fig. 4 shows, in contrast to Fig. 2, the second overcurrent relays OC5A to OC13A that operate with overcurrent of the fundamental wave current, contact THY-1b indicating that the thyristor converter THY is stopped, and the alternating current of the thyristor converter. An auxiliary contact CB2-1b has been added that closes when the power supply system disconnector CB2 is open. In Fig. 4, the contacts OCA that operate due to overcurrent of the second overcurrent relays OC5A to OC13A are connected from the control power supply bus P in parallel, and the contacts THY-1b and CB2, which close when THY is stopped, close when they are open. It is connected to one end of the tripping coil TC of the harmonic filter system shield breaker CB1 via the auxiliary contact CB2-1b, and the other end of TC is connected to the control power bus N. On the other hand, the contacts OC of the first overcurrent relays OC5 to OC13, which operate due to overcurrent during harmonic current, are connected in parallel from the control power supply bus P, and are connected to the tripping coil TC of CB1.
connected to one end of the In addition, the contacts INST that operate in the event of a short-circuit accident at OC5 to OC13 are connected in parallel from the control power supply bus P, and are connected to the tripping coil TC of CB1.
connected to one end of the In Figure 4, when the thyristor converter THY, which is the source of harmonics, becomes overcurrent during operation, overcurrent contacts OC5 to OC13, which are set based on the rated current of the harmonic filter, operate. Then, a circuit of P→OC→TC→N is constructed and CB
Similarly to the conventional method, the INST of OC5 to OC13 operates to trip CB1 in the event of a short circuit accident of OC5 to OC13. On the other hand, when the thyristor converter THY is stopped or when CB2 is open, no harmonics are generated and only the fundamental current flows through the harmonic filter. At this time, the signal THY-1b when THY is stopped or the auxiliary contact CB2-1b of CB2 is closed.
When an overcurrent occurs during fundamental wave current, a second overcurrent relay is set based on the fundamental wave current value.
Contacts that operate with overcurrent of OC5A to OC17A
OCA operates and P→OCA→THY→1b→TC→
A circuit of N or P→OCA→CB2→1b→TC→N is configured to trip CB1. As explained above, according to the present invention, when the harmonic filter is also used to improve the power factor for the fundamental frequency, it is possible to obtain an overcurrent protection device for a harmonic filter that can also provide overcurrent protection for the fundamental frequency.

[Brief explanation of the drawing]

第１図は従来の保護装置を用いた電源系統図、
第２図は従来の高調波フイルタの過電流保護回
路、第３図は本考案の一実施例を示す電源系統
図、第４図は本考案による過電流保護回路であ
る。 CB１，CB２，CB３…しや断器、CT５，CT
７，CT１１，CT１３…変流器、OC５，OC７，
OC１１，OC１３，OC５Ａ，OC７Ａ，OC１１
Ａ，OC１３Ａ…過電流継電器、Ｃ５，Ｃ７，Ｃ
１１，Ｃ１３…高調波フイルタコンデンサ、Ｌ
５，Ｌ７，Ｌ１１，Ｌ１３…高調波フイルタリア
クトル、Ｔ…サイリスタ変圧器、THY…サイリ
スタ変換装置、Ｍ…直流電動機、OC，OCA…過
電流動作接点、INST…瞬時動作接点、TC…引
外コイル、THY−１ｂ…THY停止時閉接点、
CB２−１ｂ…CB２開時閉接点。 Figure 1 is a power supply system diagram using a conventional protection device.
FIG. 2 shows a conventional harmonic filter overcurrent protection circuit, FIG. 3 shows a power supply system diagram showing an embodiment of the present invention, and FIG. 4 shows an overcurrent protection circuit according to the present invention. CB1, CB2, CB3...Shiya breaker, CT5, CT
7, CT11, CT13...Current transformer, OC5, OC7,
OC11, OC13, OC5A, OC7A, OC11
A, OC13A...Overcurrent relay, C5, C7, C
11, C13...Harmonic filter capacitor, L
5, L7, L11, L13...harmonic filter reactor, T...thyristor transformer, THY...thyristor conversion device, M...DC motor, OC, OCA...overcurrent action contact, INST...instantaneous action contact, TC...tripping coil , THY-1b...THY closed contact when stopped,
CB2-1b...CB2 open/close contact.

Claims

[Scope of utility model registration request]

An overcurrent protection device for a harmonic filter in a power system in which a thyristor converter which is a source of harmonics, a normal load which passes a fundamental current, and a harmonic filter are connected in parallel, the overcurrent protection device for a harmonic filter comprising a first overcurrent relay which operates in response to a harmonic overcurrent of the harmonic filter, and a second overcurrent relay which operates in response to an overcurrent of the fundamental wave, the harmonic filter being cut off by the operation of the first overcurrent relay while the thyristor converter is operating, and by the operation of the second overcurrent relay while the thyristor converter is stopped.