SurgeCalc - Siemens TPS3 SPD selection guide

This guide identifies a facilities surge susceptibility profile from the results of our succinct questionnaire. These results generate a surge index, which is used to aid in the selection of properly sized SPDs for each IEEE facility location (C, B, and A).

Selection Steps

  • Answer each question by selection the appropriate answer from the corresponding pull down menu.
  • At the end of the questionnaire is an IEEE category selection pull down menu. It is defaulted to category C, which is for service entrance locations. Click on submit to see the TPS3 service entrance recommendations.
  • For category B and A locations, click on category pull down menu, and select the appropriate category.
    Once the new category is selected, click on submit, and new recommendation will be shown.

Most consultants will print out the results and include them with their project file.

With the help of SurgeCalc’s susceptibility profiling, consultants can quickly find a calculated recommendation instead of just guessing or relying on a manufacturer’s representative’s recommendation.

If you need further assistance, please contact the TPS3 technical support group at 888.333.3545.

1. Geographic location of the facility.

Isokeraunic Map Canada This can be determined by consulting an Isokeraunic map and finding the location of the facility. The Isokeraunic map will show the number of days lightning is experienced for any given location. Once this is done, using the IEEE classification, rate the location for high, medium, or low exposure.

2. Facility location relative to other buildings.

If the facility is in a rural location isolated from other structures, or on a hilltop the probability of a lightning induced surges is much higher than in an urban environment.

3. Adjacent Structures.

If the facility has a large antenna, water tower, or is the tallest building in the area it has a higher probability than a facility nestled among other structures.

4. Location of the facility on the utility service.

If the facility is on the end of the utility line, surges will travel down the transmission line, or if there are other large industrials on the same line, surges could be introduced on the line by these endusers as well.

5. Utility history for an existing facility or for facilities being served by the same utility of a planned facility.

If there has been equipment disruption or equipment damage in an existing facility this is an indication of a high probability of transient activity. If this is a new facility, an inquiry to other facilities served by the same utility will give an indication of surge activity.

6. Consideration of the equipment being protected and the function this equipment performs as it applies to the facility mission.

If the equipment is supporting mission critical functions such as an on-line database, a continuous process control application, life support equipment, or other equipment that is essential for the operation of the facility it should have a high level of protection.

7. Expense to repair equipment.

If there is equipment within the facility that is very expensive to repair if damaged, such as MRI equipment, network controllers, CNC machinery etc. the level of protection should be high to avoid expensive repair bills.

IEEE C62.41 Category:

Before printing results, change print setup to LANDSCAPE mode. Also, set your margins to 0.3 Inches.

Recommended TPS3 SPDs

IEEE C62.41   Exposure Index =

Internally Mounted
Externally Mounted


Facility Exposure (Application Level)

Calculated Exposure Index

IEEE C62.41.1 Low Exposure

Exposure Index <35

Medium Exposure

Exposure Index 35 to 65

High Exposure

Exposure Index > 65

Category C (Service Entrance) 100kA to 200kA 200kA to 300kA 400kA to 500kA
Category B (Distribution Panel) 100kA to 200kA 100kA to 200kA 200kA to 300kA
Category A (Individual Circuits) 50kA to 100kA 50kA to 100kA 50kA to 100kA

Maximum Redundant Applications

IEEE C62.41.1 Low Exposure

Exposure Index <35

Medium Exposure

Exposure Index 35 to 65

High Exposure

Exposure Index > 65

Category C (Service Entrance) 200kA to 300kA 400kA to 500kA 600kA to 1000kA
Category B (Distribution Panel) 100kA to 200kA 200kA to 300kA 500kA to 800kA
Category A (Individual Circuits) 100kA to 200kA 100kA to 300kA 400kA to 500kA

Surge Protection Terms and Features

Redundancy Redundancy is the real meaning of surge current capability. As cited in our presentation and technical papers, the IEEE limits the maximum service entrance surge exposure to roughly around 10kA. This means that today's SPDs with their large kA ratings reaching 1,000,000 Amps will never be exposed to surge currents near their nameplate rating.

Thus, the nameplate kA rating is a redundant rating above the IEEE 10kA maximum. For example, a 150kA per phase surge protector is a 15 times redundant system.
Maximum Redundancy This is the largest kA ratings Siemens recommends to be applied to systems in North America. The maximum surge current rating at this level is 500kA per phase, which is 50 times the IEEE's service entrance maximum surge.
Super Redundancy There are some clients who desire the highest amount of redundancy. Siemens provides suppressors which are double of our maximum redundancy levels. These devices max out at 1000kA/phase.
Modular Suppressors Modular suppressors are suppressors that can be replaced in the field without replacing the entire suppressor being replaced. These units are configured with either a single replaceable module or with multiple modules.
Non-Modular Suppressors These are throw-away suppressors. Once these suppressors give up their lives protecting load equipment, they can't be repaired. They need to be replaced and the bad unit is tossed away.
Budgetary Suppressors Budgetary suppressors provide similar protection as our standard units, but they may have lower surge current ratings and/or reduced monitoring capabilities.
IEEE Surge Exposure Categories - C, B, and A IEEE Categories IEEE C62.41.1 and IEEE C62.41.2 describe a facilities surge voltage and current exposure levels based upon electrical distribution locations. Just like fault currents, surge current magnitudes are reduced as it travels further within a facility. This is due to the increasing impedance opposing the flow of surge currents. To better describe this concept, the IEEE developed the following "location categories:"

Category C - Parts of the distribution system that is located outside the facility and including interior sections that include revenue metering up to the line side of the main overcurrent protection device.

Category B - Parts of the distribution system that starts at the load side of the main overcurrent device and includes major feeders, and short branch circuits.

Category A - Parts of the distribution system that includes long branch circuits and receptacles.