Ground loop insulation for live events

Hello, friends.
New guy here, although I'm not new in the field of audio/video/TV production and equipment.

I was looking for answer, but couldn't find one so far, so I started a new thread, I hope it's ok.
I need to ask you for advice.

We are small company. We are doing live broadcasting from sports events. One of the main things is that, along with broadcasting, we need to send signal to video screens around the hall. There is a problem - the lights use 2 or 3 phases of the electric power. We and the sound guys use one (usually the same). It's good to be separated from the lights, but even if we are, there is a high risk - the stage construction is usually not well insulated or grounded, so there could be electric shock or higher voltage between our equipment and other equipment, that can damage it. Using the same power source is always good decision, but in some cases it can't happen, so I need to find another way to protect our equipment - we recently bought plenty of BM equipment and we don't want to destroy it. I know there are devices called ground loop insulators....english is not my native language, so I'm not sure that's the right name, but I think you understand - I need a way to protect our equipment, if the screen (that receives video signal from us) is powered by different electric phase. We will probably send SDI signal, although sometimes they need HDMI. I think I can get one SDI-HDMI converter, but I'm not sure if it is ok to have long HDMI cables. Although I work a lot in this field, I never had to send videosignal on a long cable to screen, so I'm not really sure.

Any advices will be appreciated. Thanks!

I think the proper way is using fiber. It is expensive, yes, but You avoid all grounding problems at once and long run is much better and trouble free. HDMI is no-go in any lenght, mostly because statics sensitivity.

Simply use Fiber for all connections to outside equipment. That is the best protection.

Cheers

Robert

You can protect your equipment by using fiber optical connections between your control room and the rest of the world. With this, you will not have any electrical connection and so also no problem with high voltage peaks.

When you produce sports, you may have long ways to the cameras. So fiber would have a second advantage - long cable runs up to many miles/kilometers.

For audio, you may use DI-boxes with ground lift, or also optical connections. I don't know your budget, but low budget my idea would be the usage of optical SPDIF/TOSLINK converters. (Sorry, maybe there will be better solutions for audio, it is not my primary skill).

EDIT: For bringing video to some monitors (or the first of a chain), you may use cheep "china" SDI-optical-converters. HDMI is not designed to go over distances more than 5m. With some "tricks",you can increase the distance. But there is a distance, where cost for such a HDMI cable becomes more expensive than a fiber connection including connectors....

For audio i would recommend lightpipe too if galvanic separation is must. It depends from configuration, but most inexpensive and troble free (allmost, TOSLINK cables and connectors are somewhat fragile) is using couple of ADA8200's.. (8 channels per pair)

Of course, if digital snake or something more complicated is used there is another story. But as far as i know, ethernet based connections is not 100% foolproof, at least in low price world (AES50 etc)

Good DI boxes costs more (per channel), than these Behringer converters. But of course, it depends, what You need.

Thanks a lot for all the answers so far. I have to explain that we don't have broadcasting truck/trailer - it's way above our budget. We were hiring equipment from rental company before, but we started buying our own equipment and we are building small mobile broadcasting system, installed in few racks and cases. Put everything in the van, bring it inside the hall, assemble and connect. Then disconnect and put everything back. This is the way we worked before with rental company and this is the way we'll work in the future - we stay close to the cameras and screen, so I'm not planning to have more than 100 meter cables (some of the cameras) and usually we have space close to the screen and the sound guys, so the cables are not so long. However, we still prefer not to have common connection, so I use some DI boxes for the sound. As for the video - they usually ask for HDMI or composite.

I see this solution (please correct me if I'm wrong)
I can get the SDI out of my ATEM switcher and connect it to SDI-optical converter. Then I have optical cable and then I have optical-SDI converter, but the second one must be powered by the screen guys power source. Friend who works for rental company, told me there is one BlackMagic device that makes the optical insulation inside....so it's like the 2 converters and the optical cable, together in one box. But he couldn't remember the model and I also couldn't find it. Any ideas? After the second converter (if I use 2), I can put SDI to HDMI/composite converter (depends what the screen guys want).

p.s. Maybe I have to give more details about our work, so you can get better idea what I need. Usually we broadcast different fighting sports (karate, MMA, box, kickboxing, etc). We usually have one camera above the ring, two cameras on two opposite sides of the ring and one more camera showing more crowd, hall, background, etc. We are somewhere close. The sound and the screen guys usually are also close.

Am I right, that you send video to the "house" ?

Ok power your cameras from your "control room" or use battery/accu. 50m power cable don't cost so much.... When audio-people are near to you, get your power from there. Your video hardware don't need so much, most the PCs.....

Using DI-Booxes are never wrong

Sdi is all but impervious to any issues that used to impact composite transmission. Back in the day you would use a humbucker and they were commonplace with long runs as were ground lifts when using composite. Modern lighting doesn’t use analog/copper dimmers anymore. I think you’re worrying about a problem that doesn’t exist anymore. Even so phase difference is not the issue, most large venue display requires 3 phase power or at least 2 of them, its the voltage between the ground and neutral that presents an issue. Analog audio is a different story altogether 50/60hz is a very real frequency for that medium, for 1.5ghz video transmission it’s another plane of existence.

Yes. I send video to the house. And yes - my plan is to power the cameras on batteries or with power cords (connected to our socket). And yes - I always try to get power from the sound guys. DI is always good, even if you use the same power source with the sound guys.

Speaking honestly, I have 15 years of experience working in TV and broadcasting live (and recording) different events (sport, music, etc). I also have experience working in mobile broadcasting trucks (mostly technician and soundengineer). Most of my experience is with analog audio and analog (composite) video equipment or with older video formats. But I'm still new (but not novice) in the field of HD broadcasting and our equipment is not cheap, so I'm trying to be extra careful with everything.

So, any advice from you is highly appreciated

Sdi is all but impervious to any issues that used to impact composite transmission. Back in the day you would use a humbucker and they were commonplace with long runs as were ground lifts when using composite. Modern lighting doesn’t use analog/copper dimmers anymore. I think you’re worrying about a problem that doesn’t exist anymore. Even so phase difference is not the issue, most large venue display requires 3 phase power or at least 2 of them, its the voltage between the ground and neutral that presents an issue. Analog audio is a different story altogether 50/60hz is a very real frequency for that medium, for 1.5ghz video transmission it’s another plane of existence.

Thank you (I didin't see your message, before posting the previous one).
As I said, I'm a bit new in the field of modern day / HD broadcasting. According to my experience, people still use different type of light equipment. One of the events I've done recently (with other equipment), I wanted to protect my audio cables from too many people walking on them, so I put them in cable defenders along with the control and power cables for the lights. The hum was so strong, I had to take out the audio cables and put them somewhere else. Another issue is that many of the events I do, are with equipment brought to 'the house" specially for the event. It's easier and cheaper to mount the screen on the same rig as the lights, so most of the people do it. The rig is not always well grounded and it gives me huge issues. Once I was holding one of my audio cables and touched the construction of the light rig. I had small electric shock Well, I guess there was some voltage between ground and neutral (or lets call it phase difference....sorry , my english is not so good when it comes to technical talks). So, can this voltage damage my equipment? In my case it would be the SDI output (and what's inside) of my ATEM switcher. I prefer to be extra-careful, when I'm in charge.