DFA Technology FAQs
This information serves to offer a fuller explanation of the DFA technology. Questions are grouped logically but answers will necessarily overlap to some degree and repetition of some points is unavoidable in providing a sound reply to a given question.
Whilst long-standing, the technology is an evolving one. New questions will also continue to be asked. Thus, this FAQ sheet will be maintained current on the website below.
How it is Deployed in the Field
One unit is required per circuit, connecting to the CT’s and VT’s in place for the line. The unit is rack mounted and purposefully powered from battery-backed 12 volts DC, typically obtained from station batteries. A high bandwidth continuously-available web connection is required.
None, apart from connection to a DC supply, connection to broadband and connection to the CT’s and VT’s, DFA does not require any specific setup. Network configuration and construction has no bearing on the determination/anticipation of faults. The DFA does not require any specific time to ‘learn’ a system, although the first month following commissioning is usually used to determine the normal operating parameters of the circuit against the nominal events that are identified. This facilitates the optimization of the DFA for the system.
No. Standard CT’s and VT’s that are currently used for the circuit protection are fine; there are no other special installation requirements. The units are designed not provide an excessive burden on these CT’s and VT’s for this very purpose. Indeed, not having to install special such equipment was one of the key design parameters from the outset. Ratio details are entered but the unit performs with a wide range of normally-used such transformers.
A ‘Master Station’ server-class PC is employed in the architecture of an installation and typically in the currently-deployed installations, the Master Station resides in the USA as a ‘cloud-based’ server. The Master Station is responsible for managing the utility company’s entire fleet of DFA devices, including collection of data, aggregation of information from multiple circuits and dissemination of reports to utility personnel. It contains both software for communicating to circuit devices in substations, as well as all website-related software, and SMS messaging functionality. For large utility companies, with large circuit counts, the “Master Station” may be split across multiple physical computers (e.g. one web server, combined with a DB server, combined with a communication server, etc.).
Each substation-based circuit device continuously connects to the central Master Station via broadband Internet. Should the data line be lost temporarily, the DFA unit has a generous buffering capability to ensure data collected during the communication downtime is not lost.
12 – 60VDC, battery-backed, typically derived from station batteries.
The DFA Master Station (whether it be a cloud-based or stand-alone server) performs a variety of functions, including the following:
- It provides DFA Fleet Management functions for Customer’s fleet of DFA Devices. DFA Fleet Management relies upon a properly functioning, Customer-provided network connection between each of the Customer’s DFA Devices and the DFA Master Station. DFA Fleet Management functions include:
- Enabling the Customer to monitor the health of its fleet of DFA Devices, including detection of various problems with those DFA Devices and with Customer-provided network connections (e.g., lack of communications between a particular DFA Device and the DFA Master Station in the past week, which could indicate a problem with network service or with the DFA Device itself).
- Deploying updated DFA Device Software to each DFA Device in the fleet, as such software updates become available.
- It retrieves DFA Data from Customer’s fleet of DFA Devices.
- It makes Customer’s DFA Data available to Customer via browser-based login, protected by Customer-specific usernames and passwords. Where Power Solutions provides Customer with DFA Master Station Service, it also makes Customer’s DFA Data available to Power Solutions personnel. Browser-based sessions between users (Customers and Power Solutions personnel) and the DFA Master Station are encrypted using https.
4. It retains DFA backup data.
Importantly the master Station does not contribute data analysis functions, that taking place entirely in the field-based DFA devices themselves
This question arises from the observation that DFA and other devices both take their inputs from CTs and VTs. That is where the commonality ends, however, as non-DFA devices do not monitor or record waveform data with the sensitivity or fidelity that the DFA employs. Further, to bring data streams of the sampling frequency and noise-free resolution needed by the DFA to a remote assessment point is not practicable, cost-effective, or sensible. For further detail, the reader is urged to review the companion discussion question, “How does the DFA technology differ from other industry technologies?”
Interface, Training, And Change Management Requirements
There is no need to poll the unit manually for normal reporting and alerting to take place, with the Master Station handling that function. Events are communicated to a pre-set list of names via SMS or email. Data may be accessed at any time via the web should the user wish to interrogate the unit. Waveforms downloaded are brought in low resolution firstly and then in high resolution if sought.
The key to the conversation would be understanding specifically “What information or data” would like to be seen within SCADA? Fundamentally, the kind of data collected, analysed and supplied by the DFA isn’t SCADA data, or even typically data that is compatible with a SCADA system. That’s not just file type compatibility, moreover the physical operational process of what DFA collects, how it analyses it and then how it reports it. This aspect, as far as we are aware, is not physically or philosophically compatible with what SCADA systems require or how they work, so DNP3 compliancy may not even be viable or even possible. The protocols mentioned above are typically used for RTUs and other SCADA devices and do not meet the needs of the DFA in operation or philosophy. The DFA is designed primarily as a ‘stand alone’ system which communicates within its own dedicated structure. It is not designed to interact with any other system, or provide outputs for SCADA, and there are no plans for this functionality at this stage.
DNP3 / MODBUS were designed, primarily, to be used by industrial control systems, and as such they are generally good solutions for the kinds of communication these devices do (i.e.: SCADA - polling, synchronous, relatively low data rate, etc.). They are not designed and aren't suitable for the kinds of communication the DFA requires: asynchronous, interrupt-driven, high data rates (by RTU standards), file transfers, etc.).
IEC 61850 was designed primarily as a protocol to allow various substation devices to talk to each other in a producer / consumer multicast fashion. Again, IEC 61850 is good for what it's designed to do, but its structure tends to be geared around applications very different from DFA: primarily relaying and synchro-phasors.
DFA devices communicate using standard protocols, but protocols that are more directly suited to the kinds of communication required by DFA functionality. Specifically, DFA communication between units and the master station uses HTTPS (using TLS 1.2 for transport, with messages further encrypted by JWT where authenticity is enforced with a public / private key pair unique to each unit) and SFTP (for files). Both of these can be further tunnelled through IPSec (see the current working group in IEEE SA SO/P2030.102.1)
The makers prefer to have remote web access to data from the system but it is not essential. They offer associated support to users and it has been a popular service. Such support is included in the unit price of the DFA device.
Yes. The manufacturers include this as part of the standard support, if granted web access to do so.
Initial implementation will be followed by a training and orientation service primarily delivered by LORD Consulting with contribution also from Power Solutions LLC USA. It will include scenario modelling and training on how to turn the information provided into efficient responses on the network. It is expected that those trained will include the field operations team through to the senior engineering team. Over time, it is expected that the utility itself would develop their own experience and ability supported by Lord Consulting to monitor and interrogate the DFA data at an increasing level. A vital training contribution is via User Groups and these are being established in each country of deployment.
As the unit will uniquely inform of issues and in many cases well ahead of any other corroborating data from conventional technology or customer complaints or the like, it will facilitate a greatly enhanced level of operational response. Given the increased level of event detail supplied by the DFA, this is also the case even if an event occurs that may not have been foreseeable (such as a storm-induced issue). In addition, experience to date has shown responses often can be made in a more timely and cost-effective manner (ahead of an actual failure to follow), in daylight hours, and in a much safer manner. The improvement in line failure and outage statistics as a result of the technology can be dramatic, as will be customer and stakeholder relations.
DFA waveform files are provided in an IEEE standard (1159.3) PQDiff format. http://grouper.ieee.org/groups/1159/3/index.html
You will, through your Master Station login, have the ability to download single event waveforms in the PQDiff format. We can provide the occasional files in Comtrade format, on an as-needed basis for one off exceptional events, or we can supply you with a tool that will dump the all of the chosen PQDiff files into a CSV.
There are several main factors determining the initial uptake of DFA units. Firstly, there is a level of operationalising effort that is required and that is independent of DFA numbers. Second, there is a clear need to have sufficient installed base of DFA units to ensure an adequate flow of data from them in a sensible time period to allow their performance to be tested and assessed. Thirdly, when customers also wish to enhance the initial implementation with a special project site installation (e.g.: to gain experience on SWER circuits) enough units also need to be allocated to the project sites as well as the ‘mainstream’ ones to ensure a good assessment of the data flow. Field experience in the USA over many years of installations suggest that the initial installed base would be in the area of at least 6-10 pieces, with more optimal assessments being when 5-10% of the circuits owned by a network are so monitored.
LORD Consulting will be engaged by the local suppliers LORD Power Equipment) in NZ, Australia, and the UK, to liaise with the asset management team to select the installation sites, prepare the installation details at each site, arrange any necessary training of staff and change management required. Installation would be intended to be done by the distribution company or its preferred contractor.
LORD Consulting and PSLLC, offer as part of the purchase price a uniquely-conceived package of support to ensure the technology continues to remain a viable and relevant asset management tool. This support includes general on-going monitoring of the unit remotely with comment passed back promptly on the issues being encountered, liaison across the operational team to the engineering team to the asset management team as to outcomes and contribution of the technology, regular generic updates as to interesting results observed from various clients, and a review of the continued contribution being made by the technology. It is important to note that this service is not intended as an inclusive 24hr/365 system performance monitoring service.
Lord Consulting would be happy to supply the names of referee companies for you to contact if this is desired.
Communications and Data Security
Lord Consulting and PSLLC personnel have individual user IDs. All logins are logged. Upon request by a Customer, PSLLC can make available logs related to Customer’s data, for a nominal period of time (e.g., one week).
PSLLC performs internal penetration testing on its networks. Upon request by Customer, PSLLC can supply a list of vulnerabilities found and remediation steps taken.
PSLLC does not automatically notify each Customer of changes to servers, including use of collocated or cloud resources, but generally will respond to Customer’s request for information about current configuration.
Access to DFA Data is determined by each user’s login credentials. Customer and Lord/PSLLC login IDs have access to Customer’s DFA Data.
DFA Master Station Service is not to be deemed to be critical to operations, and Power Solutions does not represent that DFA Master Station Service will have 100% availability.
Each DFA Device contains an internal firewall which is configured to drop all connection attempts. The DFA Device’s internal firewall is not configured to log such attempts. Customer may choose to configure its own firewall in front of the DFA Device to provide additional security and monitoring.
PSLLC patches the operating system software of the DFA Master Station Service, generally within a week of patches being made available the operating system vendor. PSLLC monitors the National Vulnerability Database and MITRE's CVE database to determine the criticality of individual vulnerabilities. PSLLC does not generally notify Customer of patching activities but can make a reasonable level of information available to Customer upon specific request.
The connection between each DFA Device and the DFA Master Station is via a high bandwidth web connection which is supplied by the utility. This could be either via the substation communications or a standalone comms connection. Lord Consulting can supply high end Cell modems suitable for interface with the DFA Ethernet port to the Internet as part of the supply contract. The supplied price was for hardware only and excludes installation and the on-going communications charges/plan. The utility is fully responsible for provision and maintenance of the network connection between DFA Devices and the DFA Master Station.
Each DFA Device has a factory-assigned GUID. The Master Station maintains a white list of these GUIDs. Each DFA Device establishes and maintains a connection to the Master Station. Bidirectional data transfers use that connection. The Master Station does not initiate a connection to the DFA Devices.
DFA communications use SSL.