Common Tech Support Questions

Q U I C K   L I N K S

What decoupler ratings do I need for AC Mitigation?
Can one decoupler be connected to multiple parallel insulated joints?
My valve site shorts the CP system. What do I do to solve this?
How can decoupler placement be allowed in series in a code covered electrical grounding conductor?
What are my options for separating station CP from the power company?
Can I connect a decoupler in the neutral connection to isolate my station from the power company to isolate my CP system?
What’s the difference between Dairyland products and spark gaps/lightning arresters?

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Dairyland technical support personnel work tirelessly to ensure all your needs are met when it comes to products, applications, and general support. While we cannot exhaustively answer every question in this format, we want to put the knowledge back into your hands as often as possible. Therefore, below are some frequently asked technical questions that we receive, along with a corresponding answer and other helpful resources where applicable. Should your concern fall outside the scope of these simple answers, please do not hesitate to contact our tech support team via phone (608-877-9900) or email (TechSupport@dairyland.com).

 

What decoupler ratings do I need for AC Mitigation?

Every AC mitigation project is unique, so here are steps to determine what is needed:  First, collect data from testing or studies done on the pipeline, such as AC fault current, AC steady -state current, and any classified hazardous areas along the route. The steady-state AC current rating selected should be adequate for the range of values that can occur daily or seasonally. Several Dairyland product families have a standard 45 A-rms rating, which is normally adequate. The PCR product family has an optional 80A-rms rating. The AC fault current rating will be determined from the mitigation design report, or in consultation with Dairyland staff. However, a common AC fault rating used is 5kArms (30 cycles, 50/60Hz). Lastly, determine the blocking voltage threshold required. To select the appropriate threshold, it will depend on the type of grounding material used. For copper grounding, select the -3V/+1V and the 2V/+2V for zinc grounding.

All product ratings are listed on the Dairyland website.

There are a number of accessories that can be helpful for an AC mitigation project, and are located here. Typical accessories are a pedestal to enclose the product and an isolation switch to safely disconnect a decoupler during surveys.

Additional Resources:

AC Mitigation Application Guide

“Safety Considerations In AC Mitigation Applications”

“How Do I Know Which Dairyland Product To Use?”

 

Can one decoupler be connected to multiple parallel insulated joints?

You can use one Dairyland decoupler if joints are closely spaced, for example within 2 feet. Lead lengths must be kept as short as possible for optimum over voltage protection for lightning.  Longer leads adds inductance to the connection path, which produces large voltage drops for fast rising waveforms.

 

My valve site shorts the CP system. What do I do to solve this?

To effectively isolate a motor operated valve, a decoupler can be connected in series with the equipment grounding conductor and isolate one side of the metallic conduit to prevent a bypass. This decoupling point can be anywhere between the panel and the valve motor, noting hazardous classification within the station.

One method to address multipole shorts uses a polycarbonate enclosure to house the decoupler and create an open point in the conduit. Once all shorts to ground have been cleared, a Dairyland decoupler can be connected across the open points using a grounding hub on the incoming and outgoing conduit, placing it in series in the equipment grounding conductor, and the sheath or bonding conductor of any communications cable. Connect the positive terminal of a decoupler towards the electrical panel side or the non-cathodically protected side. The negative terminal should be connected to the cathodically protected side or the motor operated valve.

 

How can decoupler placement be allowed in series in a code covered electrical grounding conductor?

In the US National Electrical Code, NFPA 70, section 250.4(A)(5) regarding an effective ground-fault current path, requires: “Electrical equipment and wiring and other electrically conductive materials likely to become energized shall be installed in a manner that creates a permanent, low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be capable of safely carrying the maximum ground fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source.”

The key is that Dairyland decouplers were evaluated, tested, and certified by Underwriters Laboratory (UL) as meeting the effective ground-fault current path requirements, as the devices were permanent, low impedance, fault-rated devices that fail safe, meaning fail shorted. Thus, they do not compromise the grounding system whether they are functional or failed and are therefore allowed in the ground fault current path.

Once the requirements of the ground fault current path are met, a listed decoupling device can be used as section 250.6 (E) states: “Where isolation of objectionable DC ground currents from cathodic protection systems is required, a listed AC coupling/DC isolating device shall be permitted in the equipment grounding path to provide an effective return path for AC ground-fault current while blocking DC current.”

The Canadian Electrical Code, CSA C22.1 in section 10-500 defines effective grounding, similar to the NEC, and in section 10-806(1) allows certified devices to be installed in grounding conductors.

Dairyland decouplers meet these requirements and have been used in equipment grounding conductors since 1996.

Additional Resource: “The Role of DC Decouplers with Cathodic Protection Systems”

 

What are my options for separating station CP from the power company?

Grounded electrical systems can bond structures with CP to the local grounding system and ultimately to the power company grounding system due to the two grounding systems being connected at the transformer. A complicated facility receiving power can have multiple possible approaches to solving shorted CP systems.

• Decouple every bond to local facility grounding (can be extremely challenging due to so many ground connections, valves, electrical equipment, etc.)
• Decouple the facility and utility grounding systems at the disconnect panel.
• Decouple the facility and utility grounding systems at the utility transformer.

Decoupling at either the disconnect panel or at the utility transformer accomplishes the same CP isolation if done correctly. If performed at the disconnect panel, your electrician can accomplish this in conjunction with the CP staff, but every station is likely built differently, and each facility will need to be examined for the source of the short. The typical situation is that the incoming neutral, which is already bonded to the power utility, is then grounded in the disconnect panel, and we have already established that your CP system is tied to the facility grounding system. Usually, the decoupler is installed in series with the electrical grounding conductor right after neutral is bonded to the ground bus at the panel to accomplish CP isolation up to that point within the station.

An alternative is to install the decoupler at the transformer between primary to secondary neutral bond. The decoupler is installed in series with this primary to secondary neutral bond and removing one of the tank or case bonding traps to prevent a bypass. This is a highly standard location that can uniformly be addressed, but it does involve an outside party – the power company.

Additional Resources:

Decoupling From Utility Grounding Systems Application Guide

DC Decoupling from Utility Grounding Systems White Paper

 

Can I connect a decoupler in the neutral connection to isolate my station from the power company to isolate my CP system?

No. A decoupler cannot be placed in series with the neutral connection because it is a load carrying conductor and a decoupler is not approved to be installed there. Decouplers are certified and approved to be installed in series with the electrical grounding conductor, which is only meant to carry fault current and not load current.

Dairyland decouplers meet the standards per UL and C-UL for Effective Ground Fault Current Path per the following:

• NFPA 70 (US National Electric Code – NEC): Article 250.4(A)(5)
• CSA C22.1 (Canadian Electric Code, Part I): 10-002

 

What’s the difference between Dairyland products and spark gaps/lightning arresters?

For a spark gap or lightning arrester to trigger, voltage must build to a very high value, typically hundreds of volts. Dairyland products have a very low and safe voltage threshold. This provides much better protection for personnel and equipment. Spark gaps or arresters generally are not rated for any notable value of AC fault current and usually fail during AC fault events. Dairyland products have high AC fault current capability ranging from 1.2 KA to 15KA and can go even higher if needed by using multiple devices in parallel, but that is another conversation.

Additional Resource: Over-Voltage Protection: The Critical Differences Between Spark Gaps and DC Decouplers White Paper

 

Dairyland is committed to providing reliable information on products, applications, and services. Don’t see your question answered above? Our tech support team is available during our normal business hours and can be reached via phone (608-877-9900) or email (TechSupport@dairyland.com).

Another helpful resource to reference is our recently published article: “Top-10 Questions About Decouplers”