Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=0.0 required=5.0 tests=FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,HTML_MESSAGE,SPF_PASS, T_DKIM_INVALID,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 X-Spam-DCC: : mailn 1480; Body=2 Fuz1=2 Fuz2=2 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by lipkowski.org (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id v757DJcl012393 for ; Sat, 5 Aug 2017 09:13:20 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ddtCk-0001Xj-Rb for rs_out_1@blacksheep.org; Sat, 05 Aug 2017 08:08:58 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ddtCU-0001XY-5D for rsgb_lf_group@blacksheep.org; Sat, 05 Aug 2017 08:08:42 +0100 Received: from mail-lf0-x229.google.com ([2a00:1450:4010:c07::229]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1ddtCP-0006nL-0H for rsgb_lf_group@blacksheep.org; Sat, 05 Aug 2017 08:08:39 +0100 Received: by mail-lf0-x229.google.com with SMTP id d17so14388482lfe.0 for ; Sat, 05 Aug 2017 00:08:36 -0700 (PDT) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to; bh=Iq57rxlXCKY5bD2m5tR16sI8QN+57mUVzOS6xlOAkP8=; b=B3WgosuSn11s14cfcU6k6abVwP35A6b385u3oJDUS1DBJKVQM8ruCSON9HhPlrC3o0 YPws/aQTGUZpwMIsO5ZT/UowB3RuhIdQSTm6SBLhTC1Bxfor1BwFCY68GYIW1leEehnN TpJmPYeXdmfFiRIyJVF6sXwDRhp6XeGgHXSmmlndcUROAjUm10QsRAlbaPgfXHO8Ba6r n6UCy6LwmSA6LQ7Wm+wnU0FH/32Jq8Bmzloz1OSHjYduIBPqRnnpqx4G7Z8GJaH6G1du +LqhnSrUOQe0xFEn4Sdvq12lMKxADHORRgKUNQK/k2zTLbNvSYx6Dfavst7jH5F9aU+i Qecw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to; bh=Iq57rxlXCKY5bD2m5tR16sI8QN+57mUVzOS6xlOAkP8=; b=VdXKfiK59pCGWHDFDWfB8m45nXIr3ZDfe5gd77YRPvEYHhaSYy34pkcldJMWUFh+Od 9g+7+M1txPGqOT/dMHGY5IIxeuhlRCCQZXULgjCbGWukT9YR8uRquYMSaJXx2PZ6o146 HeiuR0xPli1jhzwr1FFrsuxnQ9W/6JeUW7Se7HEOD5XB+FzZqJgWCsCrtmY1fwoBtXn1 oozOyctbGs6VEZN2JHVSl/qqQBfL1NJjDaDU/5xOXiD6QhOo+7ai9lQWbuZLtPzhti6B r1amgskjehdwR2MfKnX2rNBsiw69k1viut4QvX1vbZ6P4SSsKs6t5H8msvd8dkk0fibQ BpPQ== X-Gm-Message-State: AHYfb5iwYHihqV5+gFFOEL/bdl/vD8baKo3Fj6G+m2G0drEZSKkNfnTG QgHzDtNMt1AJHN2zaKWYLcuMoV8cXKsn X-Received: by 10.25.59.213 with SMTP id d82mr1328366lfl.37.1501916914675; Sat, 05 Aug 2017 00:08:34 -0700 (PDT) MIME-Version: 1.0 Received: by 10.25.22.169 with HTTP; Sat, 5 Aug 2017 00:08:33 -0700 (PDT) In-Reply-To: References: <0883B95D3F4D417F975C59A900E1A838@gnat> <3D9A092BFA65418DBEE13188A4C58580@gnat> <92ce2c22-a887-bb8f-6bc2-6f03b51899d6@t-online.de> From: Andy Talbot Date: Sat, 5 Aug 2017 08:08:33 +0100 Message-ID: To: rsgb_lf_group@blacksheep.org X-Scan-Signature: 982d53dbb4bb82e9ed4f38562b2a1556 Subject: Re: LF: G4HUP aerial current meter/ hazards Content-Type: multipart/alternative; boundary="94eb2c148b842e75e40555fc4810" X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-Scanned-By: MIMEDefang 2.75 Status: RO X-Status: X-Keywords: X-UID: 12330 --94eb2c148b842e75e40555fc4810 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Leaving the secondary of a current transformer open-circuit once caused half a city to be blacked out when the 400kV grid network tripped http://www.g4jnt.com/Hams_Hall_Investigation_Report.pdf Quite a long report, but well worth a read. Paragraph 69 covers the findings that smoke was coming from the control equipment as a current transfomrer hadce been withdrawn from servicwe, but left in place witho O/C secondary. Andy G4JNT On 5 August 2017 at 07:53, Wolfgang B=C3=BCscher wrote: > ... and never forget to wind a 'secondary' over the current transformer, > always terminated with low resistance. Otherwise you will quickly saturat= e > it, which is something that NO current transformer will tolerate at > moderate levels ! > Running a current transformer with an "open secondary" (or non-existing > secondary) should be avoided. > > Cheers, > Wolf . > > Am 05.08.2017 um 07:38 schrieb Dr. Wolf Ostwald: > >> good morning ! >> a current transformer with ferrites of unknown origin and virtues is a >> very risky thing. >> As these cores are widely available on swapmeets its a lure to use them. >> But they can be tested. I blew a few of them by just putting them on wit= h >> a single primary turn and with power less than a hundred watts they got = hot >> and broke. >> The losses can be extremely high. >> It does not help to measure their magnetic constant. As that has not muc= h >> to do with frequency dependent losses. >> a way to find out is to use a 50 ohm load and measure the RF voltage >> across the terminals. Then u just put the toroid over the "hot" side of = the >> resistor terminals. >> If the measured RF voltage drops heavily, the core is useless. You dont >> want it to block, u want to derive some RF for measuring purposes. >> The above core would go into pieces and additionally as it poses a high >> inductance to ur feedline, the amplifier stage may go south, depending o= n >> the safety factor involved with ur construction . >> >> 73 de wolf df2py >> >> > > --94eb2c148b842e75e40555fc4810 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Leaving the secondary of a current transformer open-circui= t =C2=A0once caused half a city to be blacked out when the 400kV grid netwo= rk tripped


Quite a long report, but well worth a = read.=C2=A0 Paragraph 69 covers the findings that smoke was coming from the= control equipment as a current transfomrer hadce been withdrawn from servi= cwe, but left in place witho O/C secondary.

Andy = =C2=A0G4JNT

On 5 August 2017 at 07:53, Wolfgang B=C3=BCscher &l= t;dl4yhf@freenet.de<= /a>> wrote:
... and never forge= t to wind a 'secondary' over the current transformer, always termin= ated with low resistance. Otherwise you will quickly saturate it, which is = something that NO current transformer will tolerate at moderate levels ! Running a current transformer with an "open secondary" (or non-ex= isting secondary) should be avoided.

Cheers,
=C2=A0Wolf .

Am 05.08.2017 um 07:38 schrieb Dr. Wolf Ostwald:
good morning !
a current transformer with ferrites of unknown origin and virtues is a very= risky thing.
As these cores are widely available on swapmeets its a lure to use them. But they can be tested. I blew a few of them by just putting them on with a= single primary turn and with power less than a hundred watts they got hot = and broke.
The losses can be extremely high.
It does not help to measure their magnetic constant. As that has not much t= o do with frequency dependent losses.
a way to find out is to use a 50 ohm load and measure the RF voltage across= the terminals. Then u just put the toroid over the "hot" side of= the resistor terminals.
If the measured RF voltage drops heavily, the core is useless. You dont wan= t it to block, u want to derive some RF for measuring purposes.
The above core would go into pieces and additionally as it poses a high ind= uctance to ur feedline, the amplifier stage may go south, depending on the = safety factor involved with ur construction .

73 de wolf=C2=A0 =C2=A0df2py




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