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November 30, 2021 / Jim Fenton

Sussex Day 6: Downtime

Windmills on the English Channel

Tuesday, November 9, 2021

Somewhat at the midpoint of our trip, it was time to take care of a few things like laundry. It’s also time for the thrice-annual Internet Engineering Task Force meeting, which was supposed to be in Madrid, but is being held online (again) due to the pandemic. I co-chaired a session from noon to 2 pm local time today, so I needed to be at the hotel for that. Meanwhile Kenna and Celeste did some exploring around the little shops in the Brighton Lanes.

Our downtime day also gave us an opportunity to do some laundry. One of the attractive features of our “aparthotel” is a compact combination washer/dryer. Our room also came with a couple of detergent pods, which were unfortunately and unexpectedly heavily scented. We will be using our own detergent in the future. The dryer was slow, but it did the job.

IETF virtual venue

I am again thankful for the good internet service here; the meeting went without a hitch (my co-chair is in Melbourne, Australia). Kenna and Celeste brought lunch from Pret a Manger to eat between meeting sessions I needed to attend. Following the second session we went off for dinner at a pizza place we had discovered, Franco Manca. The pizza and surroundings were outstanding; we would definitely return (and Celeste probably will). We then saw Celeste off to her bus back to campus and we returned to our hotel.


This article is part of a series about our recent travels to southern England. To see the introductory article in the series, click here.

November 29, 2021 / Jim Fenton

Sussex Day 5: Lewes

Monday, November 8, 2021

We started our day fairly early, getting a quick Starbucks breakfast before getting on the bus to University of Sussex to meet Celeste at 9:30 am. Celeste has an hour-long radio show, “Oops That Had Banjos”, on the campus radio station, University Radio Falmer. She invited us to co-host the show. The studio was exactly as I had imagined, and it was a lot of fun doing the show with her. We each contributed a couple of songs to the playlist, and got to introduce them briefly.

After the show, Celeste had classes so we continued on to Lewes. We hadn’t been able to see much on our short visit Sunday evening. We started out at Lewes Castle & Museum, again getting an idea of the history of the place and then visiting portions of the castle itself. It was a clear day, and the view from the top was excellent. As with many of these sites, the castle went through many changes through the centuries as political conditions changed.

After climbing around the castle, we were ready for lunch. We checked out a few restaurants in town before settling on the Riverside Cafe, in an attractive area on the River Ouse. After lunch, we walked among a number of small shops before entering a Waterstones bookstore. How we miss spending time in quality bookstores! I expect we’ll be seeking them out more once we return.

We then took the train back to Brighton, since I had a meeting to attend for work. The meeting went well; the internet connection at the hotel is solid and makes it seem like it hardly matters where in the world I am when attending these meetings.

Celeste came down to Brighton to have dinner with us. We decided to go with Latin American food at a local chain called Las Iguanas. The food was quite good although somewhat standard, at least to those of us from California and Colorado.


This article is part of a series about our recent travels to southern England. To see the introductory article in the series, click here.

November 28, 2021 / Jim Fenton

Sussex Day 4: Hastings

Sunday, November 7, 2021

Having gone west to Chichester yesterday, today we went east to Hastings, notable for the Norman conquest of 1066 (although the actual Battle of Hastings was some distance inland). We arranged to meet Celeste on the train as we passed through Falmer, where her campus is located, for the hour-or-so trip along the coast. Unfortunately, it seems like it’s an hour train ride to most sights outside Brighton.

Hastings is an attractive and somewhat touristy town, along the Channel and in a narrow valley surrounded by substantial hills. We walked through the town, stopping for a fish and chips lunch along the way, and admiring the small shops in the Old Town. We took a funicular up one of the two hills and had an excellent view of the surrounding terrain. Unfortunately, the ruins of the castle at Hastings were closed for the season.

After returning via funicular, we continued through the town to the Hastings Museum, a well curated (and free!) small museum that was thorough in its coverage of the history of the area, from the Iron Age to the present. It also included an extensive collection from a local family that sailed around the world in the 1800s.

Taking the train back, we had a change of trains in Lewes, which Celeste had visited and enjoyed previously. We stopped at the Lewes Arms pub, but unfortunately (since it was Sunday evening) the kitchen had closed so we couldn’t get food. So Celeste returned to campus and got dinner there, while Kenna and I got take-out chicken sandwiches to eat in our hotel.

Our weekly family Zoom conference is on Sunday evening, England time, so we ate our sandwiches while chatting with other family members back home. It’s so much easier to stay in close touch with family while traveling than it was just a few years ago.


This article is part of a series about our recent travels to southern England. To see the introductory article in the series, click here.

November 27, 2021 / Jim Fenton

Sussex Day 3: Chichester and Fishbourne

Saturday, November 6, 2021

After a pleasant breakfast at a cafe in The Lanes, we met up with Celeste at the Brighton train station and rode to Chichester, about an hour to the west. Chichester is a pleasant (and yes, touristy) town with a notable cathedral. Arriving somewhat late, we walked through the town and then found lunch at a small restaurant on a side road as many of the major restaurants in town were quite crowded (it is a Saturday, after all).



One of the main attractions in the area is the Fishbourne Roman Palace, one village to the west. We set out on foot, through a bit of rain, for a walk of a couple of miles. But when we arrived it was well worth the trip. This is an actual Roman palace, constructed in about 79AD, that had been uncovered starting in the 1960s, along with many coins, implements, and other artifacts. The mosaic floors were large and particularly impressive. As a teenager, I got to visit the ruins in Pompeii; these were of a similar nature. This palace and surrounding settlements were key to the Roman development of infrastructure in England.

Returning from Fishbourne to Chichester, we made a short visit to Chichester Cathedral. Unfortunately, the sun had set and it was difficult to see most of the stained glass. At the time of our visit, there was a large model of the Moon, traveling to several locations in Europe, that was hanging from the ceiling in the middle of the church. It was a striking thing to see, especially as we first entered.

After our train trip back from Chichester, we parted with Celeste who returned to campus. Since it was a Saturday night, restaurants were crowded, but we were able to get dinner at a large chain pub, Wetherspoons. The pub was noisy and table service was minimal. We ordered via their website and they only cleared the previous patrons’ dirty dishes when they delivered our food. The food was acceptable, but nothing to blog about.


This article is part of a series about our recent travels to southern England. To see the introductory article in the series, click here.

November 26, 2021 / Jim Fenton

Sussex Day 2: Guy Fawkes Day

Friday, November 5, 2021

These days, “day 2” after arriving in the UK has a special implication: it is on this day that you must take and report the results of a COVID-19 test. As required, we ordered the tests and had them delivered to our hotel. After breakfast (in our room/apartment, with groceries we picked up previously), we very methodically followed the instructions and 15 minutes later happily had negative test results. You send an image of the test stick next to the information page from your passport and a little while later they send a certificate of your test results. Presumably the results were sent to the authorities as well so they don’t come looking for us.

Celeste had classes at various times (including an 8:30 pm meeting with the Theater Department in Colorado) so Kenna and I were on our own today. We set out to explore Brighton, a city that bears resemblance to both Santa Cruz and Berkeley, California. We took a rather long walk, beginning with the shore area. We walked out to the end of Brighton Palace Pier, which includes a sizable game arcade and a small amusement park with rides at the end.

We decided to continue eastward along the shore and walked a long path toward Brighton Marina. Along the way were a variety of activities, including miniature golf, a sauna, an outdoor studio including a yoga class in session, and an electric railway. There was also quite a bit of construction, which makes sense since it’s off-season.

We arrived at the marina not entirely clear on how to approach it by foot: the major building we saw was a large parking garage. So we continued along the Undercliff Trail, the cliffs being primarily chalk. This is how we picture the White Cliffs of Dover must be (although Dover probably has higher cliffs). At the far end of the marina we found a pedestrian entrance, and walked back through the marina to find some lunch. We ate outdoors at Taste Sussex, which was quite good, although our seating area got a little chilly once the sun fell behind a nearby building.

Our return took us through the areas of the marina that didn’t look very pedestrian-friendly, but were actually OK. We took a different route back to the hotel through the Kemptown District. We’re not sure we found the main part of Kemptown but we did walk past the Royal Sussex Hospital.

We had heard about the Brighton Toy and Model Museum, and had a little time so we went looking for it. The maps indicated that it is located adjacent to the train station, so we went to the train station and wandered around for quite a while before discovering that it’s sort of under the station, accessed through a door on the side of an underpass. The museum is physically small, but they have a very extensive collection of classic toys and model trains, primarily from the early 20th century. The staff was helpful and friendly, even offering suggestions for what else to see while in the area.

We had a late lunch, so instead of going out for dinner we opted for wine/beer and a charcuterie plate from the small bar in the hotel. It included a couple of unusual cheeses (a black-colored cheddar, for example) and met our needs well.

Guy Fawkes Day is traditionally celebrated in the UK with bonfires and fireworks displays to commemorate his 1605 attempt to blow up Parliament. Although our room faces the Channel, we heard but had limited visibility to various fireworks being set off on the shore. So we again set out on foot and saw a few, but since the fireworks are unofficial (set off by random people on the beach), they were widely dispersed and unorganized.

It has been a good day for walking, with over 10 miles traveled.


This article is part of a series about our recent travels to southern England. To see the introductory article in the series, click here.

November 25, 2021 / Jim Fenton

Sussex Day 1: University of Sussex

Thursday, November 4, 2021

As is usual for the first day following a big time change, we did not sleep well last night. The room was still too warm and we needed to open windows and get the ceiling fans to run at a reasonable (not hurricane) speed.

We got up around 7:30. The plan was for us to take the bus to the University of Sussex and meet Celeste at 11:00, following her morning class. We grabbed breakfast at a nearby fast-food restaurant, Leon, which was good but a bit spicier than we expected. We found that we had time to stop at a nearby Marks & Spencer store for groceries; visiting grocery stores in different countries is one of our favorite tourist activities. We purchased some groceries for our kitchen, dropped them off at our room, and caught a 10:30 bus to Falmer, where the University of Sussex is located. Bus fare, as with just about everything else, is paid for by tapping a credit card (or ApplePay in our case) on the reader. But pricing is distance sensitive, so you should tap again when you get off so you don’t pay maximum fare. We didn’t tap off, so we got overcharged a bit.

A short walk took us to Falmer House, where we met Celeste. Falmer House is the Students’ Union building, although here Students’ Union has a more literal meaning than we are accustomed to: it is also an organization that advocates on behalf of the student body, even calling strikes if necessary.

We walked through campus, visiting several buildings on the way to Celeste’s dormitory at the far north end. University of Sussex was founded in 1961, and all of the buildings were of similar architecture, mostly brick. Celeste’s dormitory room is relatively spacious, with an en-suite restroom and shower. It is part of a 6-room flat that shares a kitchen and common room.

Returning to the main part of campus, we had lunch at the Falmer House deli before all three of us caught the bus back to Brighton. Kenna and Celeste explored a nearby shopping mall while I had a work videoconference. After the meeting I rejoined them and we purchased dinner from a nearby Greek food truck, the first place that we had to actually use cash. We ate that in our hotel room before Celeste returned to the University to get some school work done.

We were able to watch a TV show from our home DVR on my iPad using a VPN to our home network. Thus far we haven’t run into any of the regional restrictions on viewing video content, but we may yet. We managed to stay awake until 10:30 or 11 to try to establish somewhat of a normal sleep schedule.


This article is part of a series about our recent travels to southern England. To see the introductory article in the series, click here.

November 24, 2021 / Jim Fenton

Sussex Day 0: To Brighton

As has become somewhat traditional over the past several years, I am blogging a journal of our recent trip to the United Kingdom, our first overseas trip since the pandemic. Posts are delayed by 3 weeks from the actual events.




November 2-3, 2021

It isn’t every day that we travel to a place that the US State Department has rated as Level 4: Do Not Travel. But that’s what we’re doing today, even if that place is “only” the United Kingdom. Kenna and I are on our way to visit our daughter Celeste in Brighton, UK, where she is taking a semester abroad at the University of Sussex.

Usually we expect travel of this sort to fully occupy our day, but with the nonstop flight to London leaving San Francisco at 5:15 PM, our day got off to a leisurely start. Each of us did our usual Tuesday exercise classes, I did a bit of business work, and we got the house cleaned up a bit for our return. Our ride to the airport picked us up at 2, and we arrived in plenty of time to a virtually empty check-in counter.

One adjustment for me was that, unlike every other vacation I have been on, I did not bring a camera. I’ll be using my phone (and perhaps iPad for a few things); we’ll see how that works out. I’m sure I’ll miss my zoom lens, but I’m not sure that’s essential for this particular trip. Phone cameras are seriously good these days.

Due to some equipment problem, perhaps the entertainment system, our flight’s departure was delayed for about an hour. But once we got going, our flight proceeded smoothly (and with a minimum of turbulence, as well). Both Kenna and I got some sleep on the flight.

Our arrival at Heathrow featured the usual long walk to immigration, baggage claim, and customs. One thing that was, I think, a first for me was that the immigration process was entirely automated. Our passports were read electronically, our pictures were taken, and the gate opened without ever talking to anyone. We had our COVID-19 passenger locator forms ready, but didn’t need to present them; presumably the airline had forwarded the information when they looked at them in San Francisco or they were able to correlate the information we entered against our passport numbers.

Another brisk walk took us to the Heathrow Express station. There we purchased through tickets to Brighton, using the Two Together Railcard we had purchased prior to departure. That gave us a 30% discount for £30 a year, quite a good deal.

Heathrow Express took us to Paddington Station, from which we took the Underground to Victoria Station, which required us to lug our bags up and down a couple of flights of stairs. At Victoria we had to wait a half hour or so for our train, which allowed us to buy some sandwiches for lunch and visit a nearby bank ATM for some cash “just in case” (just about everything seems to run on credit cards these days).

We texted Celeste to let her know what train we were on, and the trip to Brighton took about an hour. We found Celeste immediately, and long-awaited hugs were exchanged before the 10 minute walk to our hotel. We are staying in a fairly new hotel, the Q Square Aparthotel (note that Q stands for Queen, not the Anon-thing). Our accommodation for the next 9 nights has a kitchen and separate bedroom, which makes it easy for us to make some of our own meals (probably breakfasts) and for me to remotely attend some of my usual work meetings. The room is great but has a few quirks: the lighting controls are unusual and the room is rather warm. But it has a balcony, and we were able to open the door for a while to mitigate the heat.

View to English Channel from our room

Kenna, Celeste, and I went for a walk to get acclimated, first to the beach, then to Brighton Palace (a local landmark) and the “Lanes”, a district with narrow, twisty roads reminiscent of the Shambles in York. We grabbed dinner at a local pub before seeing Celeste off to return to the University and returning to the hotel. Light showers had developed while we were eating, and we returned wet but not seriously soaked.

September 22, 2021 / Jim Fenton

Comments on the Federal Zero Trust Strategy

The Office of Management and Budget (OMB) and the Cybersecurity and Infrastructure Security Agency (CISA) recently released a request for public feedback on a draft strategy for a zero-trust cybersecurity architecture for the US Government in response to Executive Order 14028 issued last May. Public comments were due September 21. The comments I submitted are below.


Thank you for the opportunity to provide public comment on your draft, Moving the U.S. Government Towards Zero Trust Cybersecurity Principles. I hope that the below comments will inform your decisions as you finalize this policy.

Identity

Use of phishing-resistant MFA

Phishing is an important attack vector and must be addressed. The use of phishing-resistant MFA critically prevents the use of credentials by impostor websites and services such as mobile apps. Requiring phishing-resistant MFA by agency staff, contractors, and partners is a logical step, although existing PIV and derived PIV credentials are already phishing resistant. At the present time, PIV credentials are not available to contractors and partners that typically do not require access to federal facilities, so an alternate approach to this problem might be to unify the authentication methods used by these parties to use PIV or equivalently secure authenticators.

Requiring phishing-resistant MFA as an option for public access to federal websites and online services encourages use and familiarization with these authentication methods by the public, in addition to their direct role in blocking phishing attacks. Members of the public that adopt phishing-resistant authenticators also need to be cautioned against the use of other multifactor authentication methods that they might be prompted to use by phishing actors.

Currently, many commercial products that offer phishing-resistant authentication using the WebAuthn standard do not meet the current technical requirements of verifier impersonation resistance in NIST SP 800-63-3 (cited in footnote 4 of the draft) because they bind the authentication to the domain name of the verifier rather than to the communication channel itself. However, this non-compliance does not significantly impact the phishing resistance of these authenticators. It is widely expected that NIST will recognize these authenticators as an alternative method of achieving verifier impersonation resistance in the next revision of that Guideline. For clarity, it would be useful to explicitly recognize these authenticators as phishing-resistant in this policy as well.

Checking passwords against blocklists

This draft notes that CISA will be making a service available to check passwords against known-breached data. Use of a password blocklist is required by NIST SP 800-63B as well. The size of these blocklists should be carefully considered. A blocklist that is too small does not sufficiently protect against the use of common passwords, but a list that includes every common or breached password is likely to frustrate users, who will then focus on coming up with an acceptable password rather than other aspects of password strength such as length. There should also be the ability for individual agencies to supplement these blocklists with agency-specific entries.

The use of common passwords is not the only weakness in password use. Agencies should be reminded of the need to store password verification secrets securely (using, at a minimum, “salting” and iterative hashing) and of the need for rate limiting to blunt online guessing attacks.

Networks

DNS encryption

The draft policy notes the importance of encrypting DNS traffic, but seems to be undecided on the use of DNS-over-HTTPS (DoH, which operates in browsers) or DNS-over-TLS (DoT, which is normally implemented in the operating system). There is significant interesting DNS traffic that is not initiated by browsers, such as that coming from email clients, instant messaging applications, and many others. This policy should consider the need for DNS encryption outside the browser as well as for Web traffic.

Encryption of DNS traffic does limit agencies’ ability to inspect DNS requests for indications of malware and other inappropriate behavior, so there is somewhat of a security tradeoff in its implementation. If CISA’s Protective DNS offering is centralized, it may not be possible for individual agencies to employ DNS monitoring for security purposes.

DNSSEC

Notwithstanding the removal (by OMB M-18-23) of the requirement to implement DNSSEC that was established by M-08-23, DNSSEC implementation continues to be an effective defense against demonstrated DNS spoofing attacks and in providing a trust framework for data published in DNS. DNSSEC has a single “source of truth” that is easily monitored for fraud, unlike the WebPKI which has in excess of 100 certificate authorities, any of which could potentially publish a rogue certificate. Minimizing external security dependencies is very much in the spirit of the Zero Trust architecture. While Certificate Transparency helps a vigilant domain to detect the mistaken issuance of a certificate to the wrong party, many CAs are in jurisdictions where they could be compelled to issue a certificate and make it available to a bad actor, perhaps in support of a state-sponsored attack. For this reason, the use of DANE in addition to WebPKI, particularly for sensitive applications, should be strongly considered.

Furthermore, M-08-23 was in some cases interpreted as a requirement to DNSSEC-sign .gov domains but not necessarily to implement DNSSEC verification of DNS requests originating within an agency. In contrast many consumer DNS providers, including internet service providers and services such as Google, implement DNSSEC verification thereby giving their users a security advantage that these agencies currently do not have available. This policy should require verification as well as DNSSEC signing by agencies; verification could potentially be an aspect of the CISA Protective DNS program.

Encrypting email traffic

The draft correctly notes the importance of encryption for email traffic. It describes the use of MTA-STS to accomplish this by allowing a domain to advertise a policy that it supports SMTP-over-TLS. However, this publication requires additional infrastructure (web servers) to effect this, and requires caching of previously received policies to overcome the possibility that a bad actor will block the policy advertisement. In contrast DANE, which is deployed on DNSSEC protected domains, provides a way to publish a similar policy without this trust-on-first-use limitation and without the need to stand up additional infrastructure to support policy publication. DANE should be strongly considered as an alternative to MTA-STS for this requirement.

In addition, there is a complementary standard, REQUIRETLS (RFC 8689), that allows the sender of an email message to tag it to indicate that the message must only be sent over a TLS-protected channel, effectively overriding the opportunistic nature of STARTTLS. This most directly satisfies the stated goal of guaranteeing that Federal emails are encrypted in transit. Unfortunately, REQUIRETLS has not received significant deployment, but government interest in this capability would undoubtedly motivate deployment. REQUIRETLS builds upon MTA-STS or DANE.

Conclusion

Please do not hesitate to contact the undersigned if any further information or clarification is needed.

James L. Fenton
Principal
Altmode Networks
Los Altos, California

December 12, 2020 / Jim Fenton

Photovoltaic system updates

This past spring, I noticed that our 20 year-old wooden shake roof needed serious work. The roof condition, combined with all of the recent wildfire activity in California, prompted us to replace the entire roof with asphalt shingles. This, of course, necessitated the removal and replacement of the solar panels we had installed in 2006.

In anticipation of doing this, we consulted with our local contractor, Solar Lightworkers, to see what might be done to update the system as well as to add a bit of extra capacity since we now have an electric car. Photovoltaic technology has advanced quite a bit in the past 14 years, so we wanted to take as much advantage of that as possible while reusing components from our existing system. As described earlier, our system had consisted of 24 200-watt Sanyo panels, with half of the panels facing south and half facing west. Because these two arrays peaked at different times of day, we had two inverters to optimize the output of each array.

Design

SolarEdge inverter
SolarEdge inverter

Mark from Solar Lightworkers strongly recommended a SolarEdge inverter that uses optimizers to minimize the impact of shading of some of the panels on the overall system output. This also compensates for the fact that different panels have maximum output at different times of day. As a result, a single inverter is sufficient for our new system. We also added four 360-watt LG panels to increase our capacity. This SolarEdge inverter is also capable of battery backup, but we haven’t opted into that yet.

Since our original installation, building codes had changed a bit requiring that the panels be installed at least 3 feet below the peak of the roof. This made us rethink the layout of the existing panels. When we did the original installation, we were concerned about the aesthetics of the panels on the front of the house. But since that time, so many other houses in our area have installed solar panels that we weren’t as concerned about appearance of panels on the front (south) side of the house. We still have some panels facing west, because they seem to be nearly as efficient economically as those facing west due to time-of-use electricity pricing.

South-facing solar panels, showing 10 legacy panels in a line with 4 new (larger) panels
South-facing solar panels

Data Collection

I have enjoyed collecting data from our photovoltaic system, and have done so more or less continuously since the original system was installed, using a serial interface from one of my computers to the inverters. I wanted to continue that. The SolarEdge inverter comes with a variety of interfaces through which it can send data to SolarEdge’s cloud service, which I can view on their website. Wanting more detailed information, I found that they provide an API through which I can get data very comparable to what I got from the old inverters, and continue to analyze the data locally (as well as using their facilities, which are very good).

One of the unexpected benefits of the SolarEdge optimizers is the ability to see the performance of each panel individually. It turns out that one of the old panels had a power output almost exactly half of the others. I’m not sure how long that had been going on; perhaps since 2006. I found that the panels have a 20-year output warranty, so I contacted Panasonic, which had acquired the Sanyo product line, and filled out some paperwork and sent pictures. They sent me three very similar panels (replacing two panels with cosmetic defects as well as the one with low output) soon after. I was very happy with the service from Panasonic. Solar Lightworkers installed the new panels, and output is where it should be.

Performance

On a typical summer day with little shading, the system generated 23.7 kWh in on 8/30/2019 and 34.8 kWh (+47%) on 8/27/2020. The additional panels would account for 30% of that increase and the defective panel an additional 2%. In the late fall, the old system generated 14.6 kWh on 11/25/2019, and the new system 22.9 kWh (+57%) on 11/26/2020. There are of course other variables, such as soot on the panels from the California wildfires this year.

It will take quite a while for the increased output to pay for the upgrades, of course, but much of that cost would have been incurred just as a result of the need to replace the roof. We are quite pleased with the performance of the new system.

September 8, 2020 / Jim Fenton

Line voltage fluctuations

Voltmeter showing 101.3V

This past July, we replaced our roof and at the same time updated our solar panels and inverter (I’ll write about the new solar equipment in the near future). I was monitoring the new equipment somewhat more closely than usual, and noticed on one warm August day that the inverter had shut down due to low line voltage. Having home solar generation shut down on a warm day with a high air conditioning load is the opposite of what the utility, Pacific Gas & Electric (PG&E), should want to happen. In addition to shutting down solar power inverters, low line voltage can be hard on power equipment, such as motors.

At a time when our voltage was particularly low, I opened a low line voltage case with PG&E. This resulted in a call from a field technician that told me several things:

  • PG&E has been aware of the voltage regulation problem in my neighborhood for some time
  • The problem is likely to be due to the older 4-kilovolt service in my part of town. Newer areas have 12-kilovolt service that would be expected to have about 1/9 the voltage drop with an equivalent load.
  • Another possible cause is the pole transformer that feeds our house and nearby neighbors that the technician told me is overloaded. [Other neighbors that aren’t as close are reporting these problems as well, so they would have to have similarly overloaded transformers.]
  • Line voltage at my home is supposed to be between 114 and 126 VAC.

Another technician from PG&E came out a couple of days later to install a voltage monitor on the line. But it occurred to me that I have been collecting data since 2007 from my solar inverter that includes voltage data. A total of about 3.2 million data points. So I thought I’d check to see what I can find out from that.

My data are in a MySQL database that I can query easily. So asked it how many days there have been where the line voltage went below 110 VAC (giving PG&E some margin here) and the solar inverter was fully operating. There were 37 such days, including very brief voltage dips (<10 minutes) up to over 5 hours undervoltage on September 2, 2017. The line voltage that day looked like this:

A more recent representative sample is this:

Part of my concern is that this problem seems to be getting worse. Here is a table of the number days where <110 VAC lasted for more than 10 minutes:

YearDays with
Undervoltage
Undervoltage
Minutes
200700
200800
2009114
201000
201100
201200
201300
201400
2015119
2016110
2017141386
201800
20197561
2020 (to June 30)2160

And as I mentioned above, the problem seems to occur on particularly hot days (which is when others run their air conditioners; we don’t have air conditioning). Fortunately, the NOAA National Centers for Environmental Information provide good historical data on high and low temperatures. I was able to download the data for Los Altos and relate it to the days with the outages. Indeed, the days with the most serious voltage problems are very warm (high of 110 on 9/2/2017 and 100 degrees on 6/3/2020 shown above).

Does that mean we’re seeing purely a temperature effect that is happening more often due to global warming? It doesn’t seem likely because there have been very warm days in past years with little voltage drop. Here’s a day with a recorded high temperature of 108 in 2009:

My street, and the City of Los Altos more generally, has seen a lot of extensive home renovations and tear-down/rebuilds the past few years. The section of the street I live on, which has about 50 homes, currently has three homes being completely rebuilt and currently unoccupied. So this is only going to get worse.

The ongoing renovations and rebuilds in Los Altos are all considerably larger than the homes (built in the 1950s) that they replace, and I expect nearly all have air conditioning while the original homes didn’t. This is resulting in a considerably higher electrical load on infrastructure that wasn’t designed for this. While this is mitigated somewhat by the prevalence of solar panels in our area, the City needs to require that PG&E upgrade its infrastructure before issuing new building permits that will exacerbate this problem.

SolarEdge inverter display