Brilliant brings back memories of my HV Cable Lineman course when we would pretend that the course installs were completely disconnected then the Instructor's would connect a 500V Megger to it to catch us all out 😵💫
Long time since I have seen a CDG relay in the wild. Quite delicate to set up really and required quite a high powered test set to test them, unlike the modern electronic relays. I would imagine most of the CDG were replaced by the MIDOS range, which I still see quite a lot of. Then they went to the Micom range which is the digital/numerical design. The time delay was based on an inverse curve and the modern relays still use the same formula. Should get hold of one of these one day to play with on my test set. The striker pin on the HV fuse is usually spring loaded and held back by the fuse ink inside, when the fuse link is broken the spring pushes the striker out, usually doesn't take a lot of effort to trip the striker mechanism.
I think those fuses have a long coil spring inside, held in tension by the fuse wire, so when it blows, it rapidly increases the gap to quench arcing. The spring then pushes the striker pin out.
On the CDG relay, the plug is the current setting. This relay is intended for a current transformer (CT) with a 5amp secondary current. If you use a 100/5 CT and have the plug in the 5A hole, the relay will allow 100A to pass continually. If you plug it in the 10A hole it will allow 200A etc. The relay requires usually about 20% overload to start moving. If you are set for 100A and a load of 200A ia applied, ie 2 times the setting it will take 10 seconds to trip if the dial is at 1.0. That is called a Time Multiplier and it multiplies the time by the second. If it is turned to 0.5 the in the example above it will trip in 5 seconds insted of 10s. Normally used with 3 CTs in a star arrangment with the overcurrent elements in the Red and Blue CT wires and the Earth element in the star point return.
Thanks , I would like to make this work someday maybe by winding multiple turns around a ct and see g if that works I need to get a diagram of it and tryout some point
The HV fuse is the fault breaking device. The switch it is installed in is not capable of breaking fault current. The faulty phase or phases will blow the fuse and the trip pin will open the switch to disconnect the other phases. These fuses should always be replaced as a set of three as a fault which results in different currents will blow one fuse completely but only some of the parallel elemnets within the other fuse. When you then repair and load the circuit, the weakened fuse may blow under load current.
Great video, i wanted to point out two new transformers installed on a project of mine each have an incandescent lamp inside them..... Think of the energy savings with they make that an led lamp instead 😉
12:12 - yeah.. the instrument screws will likely be BA thread form. 0BA ~ 6mm your rear stud connections. I was working with them during my apprenticeship in the 70's. Less so that EE type... lots of GE and P&B Golds. The instrument comes in 2 parts... the Case and the Relay. These are very knock sensitive instruments, so during manufacture and shipping to site, the Panel is empty cases. Relays go in long after the truck drivers and other grunt boys ship and building fitters have left the site. i.e. During commissioning. There are MUCH better Generation and Distribution Protection relays in use today.... and a shit load better HV CB's than the primitive crap shown in still pics.
Brilliant brings back memories of my HV Cable Lineman course when we would pretend that the course installs were completely disconnected then the Instructor's would connect a 500V Megger to it to catch us all out 😵💫
Long time since I have seen a CDG relay in the wild. Quite delicate to set up really and required quite a high powered test set to test them, unlike the modern electronic relays. I would imagine most of the CDG were replaced by the MIDOS range, which I still see quite a lot of. Then they went to the Micom range which is the digital/numerical design. The time delay was based on an inverse curve and the modern relays still use the same formula. Should get hold of one of these one day to play with on my test set.
The striker pin on the HV fuse is usually spring loaded and held back by the fuse ink inside, when the fuse link is broken the spring pushes the striker out, usually doesn't take a lot of effort to trip the striker mechanism.
I think those fuses have a long coil spring inside, held in tension by the fuse wire, so when it blows, it rapidly increases the gap to quench arcing. The spring then pushes the striker pin out.
On the CDG relay, the plug is the current setting. This relay is intended for a current transformer (CT) with a 5amp secondary current. If you use a 100/5 CT and have the plug in the 5A hole, the relay will allow 100A to pass continually. If you plug it in the 10A hole it will allow 200A etc. The relay requires usually about 20% overload to start moving. If you are set for 100A and a load of 200A ia applied, ie 2 times the setting it will take 10 seconds to trip if the dial is at 1.0. That is called a Time Multiplier and it multiplies the time by the second. If it is turned to 0.5 the in the example above it will trip in 5 seconds insted of 10s. Normally used with 3 CTs in a star arrangment with the overcurrent elements in the Red and Blue CT wires and the Earth element in the star point return.
Thanks , I would like to make this work someday maybe by winding multiple turns around a ct and see g if that works I need to get a diagram of it and tryout some point
The HV fuse is the fault breaking device. The switch it is installed in is not capable of breaking fault current. The faulty phase or phases will blow the fuse and the trip pin will open the switch to disconnect the other phases. These fuses should always be replaced as a set of three as a fault which results in different currents will blow one fuse completely but only some of the parallel elemnets within the other fuse. When you then repair and load the circuit, the weakened fuse may blow under load current.
Great video, i wanted to point out two new transformers installed on a project of mine each have an incandescent lamp inside them..... Think of the energy savings with they make that an led lamp instead 😉
IDMT Relay - Inverse Definite Minimum Time
You sound like Greg Davies xoxoxoxoxo
EDIT: Greg Davies sounds like you
12:12 - yeah.. the instrument screws will likely be BA thread form. 0BA ~ 6mm your rear stud connections.
I was working with them during my apprenticeship in the 70's. Less so that EE type... lots of GE and P&B Golds.
The instrument comes in 2 parts... the Case and the Relay. These are very knock sensitive instruments, so during manufacture and shipping to site, the Panel is empty cases. Relays go in long after the truck drivers and other grunt boys ship and building fitters have left the site. i.e. During commissioning.
There are MUCH better Generation and Distribution Protection relays in use today.... and a shit load better HV CB's than the primitive crap shown in still pics.
Those look more like 120's
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