HP R5000 UPS

[Simpo]

Can someone tell me what functionality is available in bypass mode and are the outlets directly connected to utility input power?

[Suman_1978]

Hi,

In general terms, Bypass mode will allow the power to pass through without going into the UPS, which means that your equipment is not protected.

Here is the UPS user guide, please refer to page# 29, 42, 44

Thank You!
I work with HPE but opinions expressed here are mine.
HPE Tech Tips videos on How To and Troubleshooting topics

[Simpo]

The reason for asking is that I need to measure Ze (external earth fault loop impedance) and I would expect the measurements to be skewed if going through a UPS socket in normal mode.

Any thoughts on the issue?

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[Suman_1978]

Hi,

No info on "external loop impedance" from HPE (I could not find).
May be if someone has this information or how to measure, may respond.

Thank You!
I work with HPE but opinions expressed here are mine.
HPE Tech Tips videos on How To and Troubleshooting topics

[Vinky_99]

@Simpo 

Good day!

The bypass mode is designed to allow utility power to flow directly to the connected equipment without any conditioning or interruption by the UPS. The primary purpose of bypass mode is to provide a fail-safe mechanism in case the UPS experiences a fault or overload condition. When the UPS is in bypass mode:

1. In bypass mode, the outlets are directly connected to the utility input power. This means that the connected devices are powered by the utility electricity without any interference or conditioning by the UPS. The UPS essentially acts as a pass-through device.

2. In bypass mode, the UPS does not provide battery backup. If there is a power outage or disturbance in the utility power, it will directly affect the connected devices since the UPS is not providing power from its internal battery.

Regarding your specific concern about measuring Ze (external earth fault loop impedance), if you are conducting electrical measurements on the utility side of the UPS while it's in bypass mode, your measurements should not be skewed by the UPS. This is because the UPS is not actively conditioning or altering the utility power in bypass mode.

However, when the UPS is in normal mode (online or line-interactive mode), it conditions the incoming utility power to provide clean, stable power to the connected devices. In this mode, the UPS regulates voltage and frequency, filters out noise, and provides battery backup in case of power disturbances. If you measure Ze from the outlets on the UPS while it's in normal mode, your measurements could be affected by the UPS's conditioning processes.

To ensure accurate Ze measurements, it's generally recommended to measure the impedance directly at the electrical distribution panel or point where the utility power enters your facility, bypassing the UPS altogether. This will give you a more accurate representation of the external earth fault loop impedance without any interference from the UPS.

Always exercise caution when working with electrical systems, especially when making measurements, and consider involving a qualified electrician or technician if you are unsure about the procedures or safety precautions required.

I hope this give some insights. Let me know.... 

[Simpo]

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Many thanks

I probably meant Zs not Ze and that is what I suspected.

I do have a concern that I'm going to be looking at though. the impedance from distribution board earth to UPS chassis seems somewhat high 2 to 3 ohms although the measurement to the PDU earths supplied from the UPS is in the region of 0.1 Ohm or lower.

UPS is in normal operating mode.

Any thoughts on the disparity, same on all my UPS.

Simpo

[Vinky_99]

Hello Simpo,

The disparity you're observing in the impedance measurements between the distribution board earth and the UPS chassis, as well as the PDU earths supplied from the UPS, could be due to a few factors.

[Vinky_99]

@Simpo 

Here are some potential reasons for the differences in impedance readings:

>> The impedance between the distribution board earth and the UPS chassis depends on the design of the grounding system in your facility. If the distribution board earth and UPS chassis are not directly bonded, there can be impedance between them. Grounding systems may incorporate grounding electrodes, ground rods, and conductors of different sizes, which can contribute to variations in impedance.

>> The length of the grounding path can significantly affect impedance measurements. Longer grounding paths, such as those between the distribution board and the UPS, may have higher impedance due to the increased resistance along the path.

>> The size and material of the conductors used in the grounding system can influence impedance. Larger conductors with lower resistance will generally result in lower impedance readings.

>> The quality of the electrical connections, including the integrity of the ground connections, can impact impedance. Loose or corroded connections can increase resistance and impedance.

>> The specific grounding practices and standards followed in your facility can also affect impedance measurements. Compliance with local electrical codes and standards is essential to ensure a safe and effective grounding system.

>> The design of the UPS itself, including the grounding connections and the internal grounding system, can influence impedance measurements. Some UPS units are designed with specific grounding provisions.

To address the disparity in impedance measurements, you may consider the following steps:

>> Physically inspect the grounding connections between the distribution board, the UPS chassis, and the PDUs. Ensure that all connections are secure and free from corrosion.

>> If you have concerns about the grounding system's design or performance, consider consulting with a qualified electrical engineer or technician who can perform a comprehensive assessment and provide recommendations for improvement.

>> Review the local electrical codes and standards applicable to your area to ensure compliance with grounding requirements. Make any necessary adjustments to your grounding system based on these standards.

>> If it's necessary to reduce impedance between the distribution board and the UPS chassis, consider additional bonding methods or conductors to establish a low-resistance path.

>> Ensure that you document all changes made to the grounding system, and implement a regular maintenance program to keep the grounding system in good condition.

It's important to prioritize safety and adhere to best practices when working with grounding systems, as proper grounding is essential for electrical safety and equipment performance.

Hope this helps! 

[Simpo]

Thanks for the answer  I am a qualified electrical engineer and more than happy with the facility grounding arrangement

 Short path, good connections on the conductors individual to each UPS, high CSA cpc etc.

I think removing a ups for bench testing may be my only way forward as they all exhibit the same reading. In may have just picked a bad chassis point to measure at

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