10 Replies Latest reply on Oct 19, 2015 12:19 AM by mcb1

    How to build an Earth (Ground) Resistance Continuous Monitoring Device?

    joomunm

      Hi All,

       

      I have never seen any Schematic Diagram for an Earth (Ground) Resistance Continuous Monitoring Device.

       

      If someone has one please share it with me.

       

       

      Thanking you before hand.

       

      Regards,

          • Re: How to build an Earth (Ground) Resistance Continuous Monitoring Device?
            joomunm

            Hi,

             

            I am looking for an Earth Resistance Continuous Monitor Device operating on 230VAC 50HZ to verity the Earth/Ground (TT system) every second. In case the resistance drops below the parameter (25~100 ohms), a visual (LED) is lighted plus an audible alarm is heard.

             

            Refer to link below:

             

            http://www.transorbelectrical.com/pq/technical/HomeShield.pdf

             

            Hope this link will be self explanatory.

             

            Thanks.

             

            Regards,

              • Re: How to build an Earth (Ground) Resistance Continuous Monitoring Device?
                ash_amby

                Hi all,

                 

                In a place which has more than 200 earthing pits for power and lightning arrestor. Weekly checks are required to be done which is a herculean tasks moreso that manpower cannot be consistent and may also sham on doing the same. I am looking for a solution where in the system can be installed for automatic checking and monitoring so that the values can be read on a daily/ weekly basis with one monitor and print of the output can be put up for validation. Does anyone know of such a system and the firm/vendor which supplies and installs the same. Finance is not a constarint

                • Re: How to build an Earth (Ground) Resistance Continuous Monitoring Device?
                  jw0752

                  Hi Mamade,

                  Can you confirm that you want to test the resistance between a piece of equipment and the Earth Ground. Your second post indicated that you wanted a visual and sound alert if the resistance to ground gets below 100 ohms. For clarification is the piece of equipment grounded or isolated from ground. Your specification for the alarm would indicate that you do not want there to be a ground circuit and want an alarm if there is a connection to Earth Ground.

                  John

                    • Re: How to build an Earth (Ground) Resistance Continuous Monitoring Device?
                      ash_amby

                      Hi This is resistance between equipment and earth. Further audio and visual warning are desired if  reading of  resistance value goes above 08 ohm.

                        • Re: How to build an Earth (Ground) Resistance Continuous Monitoring Device?
                          mcb1

                          Can you describe what the check is these people do.

                          In the earlier days we used to apply a heavy current to test that the resistance was low and more importantly that the earth lead could take the necessary current.

                          It has been raised that simply measuring the resistnace doesn't verify the connection will handle the required fault current.

                           

                           

                          You could apply a current and measure the voltage during the test.

                           

                          Mark

                            • Re: How to build an Earth (Ground) Resistance Continuous Monitoring Device?
                              ash_amby

                              Hi all,

                               

                              I was discussing the problem with my colleagues and it emerged that the similar contraption has been used and installed in smart homes which has a large number of heavy load appliances. The same is monitored and displayed in case there is a break down in the earthing. However, in these homes the power supply earth maybe only one......My issue is a bit different that I have a number of earthing points and i need a system to measure values of the resistance easily without any human errors.

                              Another thought is that Installing a sensor/ transducer in the output /where we measure values and then bring them to one monitor could be a solution but the extent of wiring through out that land area is another matter of concern. 

                              Regards

                                • Re: How to build an Earth (Ground) Resistance Continuous Monitoring Device?
                                  mcb1

                                  The same is monitored and displayed in case there is a break down in the earthing.

                                  You aren't confusing an Earth leakage Detector are you.?

                                   

                                   

                                  These detect any in-balance in phase and neutral current and disconnect the power to that circuit.

                                   

                                  As jw0752 has pointed out there are some other issues that could be introduced.

                                  Are you able to do any form of schematic to show the connections, in some form of relative way to each other.

                                   

                                  The reason is that unless you have your reference at the centre of the multiple earth rods, you may get an in-balance and current may actually flow up the earth rod, through the mains earth/neutral (in NZ/AUS the neutral and earth are the same potential).

                                  This might still register within the acceptable reading.

                                   

                                  I understand that testing is a pain, but there are good reasons why it's done.

                                  You might be able to use a low voltage high current system which you connect to the earth and measure and record each time.

                                  This will show any trend or sudden change.

                                   

                                  Many of the commercial testers have the ability to record, which removes the operator from the equation.

                                   

                                  Mark

                            • Re: How to build an Earth (Ground) Resistance Continuous Monitoring Device?
                              michaelkellett

                              I think the problem is that they need to check the quality of the connection of an earth spike (for want of better description) to actual Earth.

                               

                              It's not easy - in an installation with multiple earth spikes, like Ashish has, you could measure the resistance from one spike to all the other spikes but that is actually very difficult to do (since I assume that the installation must work without interruptions).

                               

                              MK

                        • Re: How to build an Earth (Ground) Resistance Continuous Monitoring Device?
                          jw0752

                          Hi Mamade,

                          mcb1 and michaelkellett  have made good points. If I am analyzing the physics correctly you have a problem whose solution will have undesirable side effects.

                           

                          For Example:

                           

                          To really test individual spikes you need to be able to isolate the spike from the grid.

                          Side Effect:The mechanism to isolate the spike will itself be another point of failure that will need to be tested.

                           

                          To test a spike you need a test connection to ground that is assured and at least as good as the spike being tested.

                          Side Effect: The test is testing its own connection to ground as well as the Spike's ground.. I suspect that any test of a real ground spike with a conventional meter that has a reading of 0.8 ohms, or greater, is probably just reading its own wiring and connection to ground and not the actual spike and cable.

                           

                          As Mark pointed out, just checking the Ohms to ground with a conventional ohmmeter  will not tell you if your conductor is heavy enough to handle system failure amperage.

                          Example: We can test and get 0.8 ohms of resistance to ground through a 3 meter 18 gauge wire but an 18 gauge wire may not handle the current of a system failure.

                           

                          You may find a program of scheduled replacement and refitting of the spikes might be more cost effective than testing and waiting for a failure.

                           

                          I at least can think of no magic testing circuit that will do what you are hoping for.

                           

                          John